[1] In 1867, a pre-Confederation coalition of Liberal and Conservative elements formed a permanent national party named the Liberal-Conservative Party. Although formally known as the Liberal-Conservative Party, the party was commonly referred to as the Conservative Party until 1917 and the formation of the Unionist government. With the resignation of Sir Robert Borden and the rise to party leadership of Arthur Meighen in July 1920, the party was officially renamed the National Liberal and Conservative Party. At a party conference in March 1922, the party was renamed the Liberal-Conservative Party. In March 1938, at a party conference, the party was renamed the National Conservative Party. During the general election campaign of 1940, the party was renamed the National Government Party. Following the general election of 1940, the party was again named the National Conservative Party. On December  11, 1942, at a party leadership convention which elected the former Progressive Premier of Manitoba, John Bracken, to the position of party leader, the party was renamed the Progressive Conservative Party.

[2] On May 24, 1867, Sir John A. Macdonald was formally commissioned by Lord Monck to form the first government under Confederation. On July 1, 1867, the First Ministry assumed office with Macdonald serving as Prime Minister. He died while in office on June 6, 1891.

[3] Sir John Thompson was the Leader of the Government in the House of Commons between June 16, 1891, and July 9, 1892, while Sir John Abbott governed as Prime Minister from the Senate. Upon the resignation of Mr. Abbott, Mr. Thompson was called upon to form a government and served as Prime Minister from December 5, 1892 until his death on December 12, 1894. Sir Mackenzie Bowell then occupied the position of Prime Minister from the Senate until 1896. George Foster served as the Leader of the Government in the House of Commons throughout the Fifth Session of the Seventh Parliament, April 18, 1895 to July 22, 1895, and during the Sixth Session of the Seventh Parliament between January 2, 1896 and January 5, 1896, whereupon he resigned from the Cabinet. On January 15, 1896, he was reappointed to Cabinet and again assumed the duties of the Leader of the Government in the House of Commons until February 11, 1896. Sir Adolphe Caron served as the Leader of the Government in the House of Commons from January 7, 1896 until January 15, 1896.

[4] Sir Charles Tupper entered the Cabinet of Prime Minister Mackenzie Bowell on January 15, 1896. He became the Leader of the Government in the House of Commons upon his introduction in the House on February 11, 1896 until April 23, 1896. Mr. Tupper served as Prime Minister from May 1, 1896 to July 8, 1896, and as Leader of the Opposition throughout the Eighth Parliament, from August 19, 1896 to July 18, 1900. He continued to serve as party leader until February 5, 1901.

[5] In the general election held on November 3, 1904, Sir Robert Borden suffered personal defeat. As a result, from January 11, 1905 to February 6,1905, George Foster served as Acting Leader of the Opposition in the House. Mr. Borden was re-elected in a by-election held on February 4, 1905, and returned to the House of Commons on February 7, 1905.

[6] Sir George Foster, who had been knighted in 1914, served as Acting Prime Minister from April 19, 1917 to May 15, 1917. During this period, Prime Minister Borden was in attendance at the Imperial War Conference in London. He returned to the House of Commons on May 16, 1917.

[7] Sir Thomas White served as Acting Prime Minister from February 20, 1919 to May 23, 1919. During this period, Prime Minister Borden was attending the Paris Peace Conference which followed the end of the World War I. Prime Minister Borden returned to the House of Commons on May 26, 1919. Sir George Foster served as Acting Prime Minister from February 26, 1920 to May 12, 1920. During this period, Prime Minister Borden was absent from the House of Commons due to illness. Borden recommended that the Governor General call upon Arthur Meighen to succeed him as Prime Minister. Mr. Meighen was sworn in as Prime Minister on July 10, 1920.

[8] On February 17, 1919, Sir Wilfrid Laurier died. On February 25, 1919, Daniel McKenzie was elected by the Liberal caucus to serve as leader of the Liberal Party in the House. On August 7, 1919, at a convention of the Liberal Party, W.L. Mackenzie King was elected leader of the Liberal Party. He was elected to the House on October 20, 1919, and introduced in the House on October 23, 1919. However, he did not assume the duties of leader of the Liberal Party in the House until the opening of the Fourth Session of the Thirteenth Parliament on February 26, 1920. Daniel McKenzie continued in his duties as Leader of the Opposition and leader of the Liberal Party in the House until the end of the Third Session of the Thirteenth Parliament.

[9] On February 26, 1920, at the opening of the Fourth Session of the Thirteenth Parliament, Liberal-Unionist T.A. Crerar assumed the leadership of the Progressive Party until November 11, 1922.

[10] In the general election of October 29, 1925, the government of W.L. Mackenzie King was returned to office. Mr. King himself suffered electoral defeat but remained Prime Minister. When the First Session of the Fifteenth Parliament opened on January 7, 1926, Ernest Lapointe served as Leader of the Government in the House. Mr. King was elected in a by-election on February 15, 1926, and returned to the House on March 15, 1926.

[11] Sir Henry Drayton served as the Leader of the Government in the House of Commons from June 29, 1926, to July 1, 1926. He assumed this position, when the Prime Minister, Arthur Meighen, resigned his seat in the House of Commons according to law, in order to assume the office of Prime Minister. Until August 3, 1931, and the adoption of an amendment to the Senate and House of Commons Act (R.S. 1927, c. 147), Members of the House were required to resign their seat and seek re-election when appointed to Cabinet.

[12] Hugh Guthrie occupied the position of Leader of the Official Opposition following the resignation of the party leader, Arthur Meighen, and prior to the assumption of party leadership by R.B. Bennett.

[13] J.S. Woodsworth became president of the Co-operative Commonwealth Federation, known as the CCF, in July 1933. The CCF Party was founded in Calgary on August 1, 1932. At the August 1960 convention, the party constitution was amended to create a new position, that of “national leader”.

[14] Richard B. Hanson and Gordon Graydon occupied the position of Leader of the Official Opposition because the leaders of the National Party throughout this period, Arthur Meighen and John Bracken, did not sit in the House.

[15] Due to the deteriorating health of party leader J.S. Woodsworth, M.J. Coldwell was elected to serve as acting leader of the party at a CCF caucus meeting on November 6, 1940. Shortly after Mr. Woodsworth’s death, Mr. Coldwell was elected permanent leader of the party at a caucus meeting on April 22, 1942.

[16] On two occasions, W. Earl Rowe assumed the duties of Acting Leader of the Official Opposition due to the illness of the Leader of the Official Opposition, George Drew.

[17] Following the defeat of M.J. Coldwell in the federal election of 1958, Hazen Argue occupied the position of leader of the party in the House. Mr. Argue held this position from April 23, 1958 until August 11, 1960, whereupon he became permanent national leader of the CCF at a party leadership convention. On August 3, 1961, at a party leadership convention, the existing party joined with groups representing organized labour to form a new party. As a result, the name of the party was changed from the Co-operative Commonwealth Federation to the New Democratic Party. T.C. Douglas was elected leader of the New Democratic Party. However, Mr. Douglas was not elected to the House until a by-election held on October 22, 1962, and was not introduced in the House until November 2, 1962. During this period, Hazen Argue served as party leader in the House until his resignation from the New Democratic Party on February 18, 1962. The following day, the NDP caucus elected H.W. Herridge to serve as party leader in the House. Herridge occupied this position until November 1, 1962.

[18] On September 1, 1963, 13 Members from Quebec left the Social Credit Party and formed the Ralliement des créditistes under the leadership of Réal Caouette. On October 21, 1963, the Ralliement des créditistes was officially recognized as a party by the House of Commons.

[19] Michael Starr occupied the position of Leader of the Official Opposition following the resignation of the party leader, John Diefenbaker, and prior to the new party leader, Robert Stanfield, being elected and introduced in the House.

[20] T.C. Douglas was defeated in the general election of June 25, 1968. He was re-elected in a by-election held on February 10, 1969, and introduced in the House on February 20, 1969. During his absence from the House, David Lewis led the New Democratic Party Members in the House. David Lewis was formally elected leader of the party at a party leadership convention on April 24, 1971.

[21] In 1971, the Ralliement des créditistes, who had elected to the House 14 Members in the previous general election, reunited with the Social Credit Party. On October 10 of that year, Réal Caouette was confirmed as leader of the Social Credit Party.

[22] In the general election of July 8, 1974, David Lewis suffered personal defeat. Although Mr. Lewis remained party leader until July 7, 1975, Edward Broadbent served as leader of the party in the House beginning with the opening of the Thirtieth Parliament on September 30, 1974. Mr. Broadbent was formally elected leader of the party at a party leadership convention on July 7, 1975.

[23] Erik Nielsen occupied the position of Leader of the Official Opposition following the resignation from that position of Joseph Clark, and prior to the election and introduction to the House of the subsequent party leader, Brian Mulroney.

[24] On February 7, 1990, John Turner resigned from his position as Leader of the Official Opposition but remained leader of the Liberal Party. In his place, Herb Gray assumed the duties of Leader of the Official Opposition. On June 23, 1990, at a leadership convention, Jean Chrétien was elected leader of the Liberal Party. He was elected to the House in a by-election on December 10, 1990, and was introduced in the House and became Leader of the Official Opposition on January 15, 1991.

[25] Preston Manning was leader of the Reform Party until March 26, 2000, when the party reorganized itself into the Canadian Reform Conservative Alliance (Canadian Alliance).  Deborah Grey was acting leader of the Canadian Alliance from March 27, 2000 until July 7, 2000.  On July 8, 2000, Stockwell Day was elected leader of the party at a leadership convention.

[26] Elsie Wayne assumed the functions of party leader in the House following the resignation of Jean Charest as leader of the Progressive Conservative Party on April 2, 1998. On November 14, 1998, Joseph Clark was elected as leader of the Progressive Conservative Party. Since he was not a Member, Elsie Wayne continued to serve as leader of the party in the House until Mr. Clark could be elected.

[27] Stockwell Day was party leader of the Canadian Alliance until his resignation on December 11, 2001.  John Reynolds served as interim leader from December 12, 2001 until March 19, 2002.  Stephen Harper won the party leadership at the 2002 Canadian Alliance leadership election, and served as party leader from March 20, 2002 until December 5, 2003, when the party ratified its merger with the Progressive Conservative Party to form the Conservative Party of Canada.

[28] Joseph Clark was party leader of the Progressive Conservative Party (designated in the House as the Progressive Conservative/Democratic Representative Coalition for a brief time) until his resignation on May 30, 2003. On May 31, 2003, Peter MacKay was elected party leader during the 2003 Progressive Conservative leadership convention. The Progressive Conservative Party ratified its merger with the Canadian Alliance on December 6, 2003 to form the Conservative Party of Canada. After the newly-formed party was officially registered with Elections Canada on December 7, 2003, Senator John Lynch-Staunton became acting party leader from December 8, 2003 until March 19, 2004. Stephen Harper was elected leader of the party on March 20, 2004 at a leadership convention.

[29] Alexa McDonough was party leader from October 14, 1995 until the 2003 New Democratic Party leadership convention. On January 25, 2003, Jack Layton was elected party leader, but did not become a Member of Parliament until June 28, 2004. Bill Blaikie was Parliamentary Leader during the interim, from January 26, 2003 until June 27, 2004. 

[30] On February 6, 2006, Paul Martin resigned as the leader of the Liberal Party in the House of Commons, but remained leader of the Liberal Party for other purposes. Bill Graham was appointed interim Leader of the Opposition. On March 18, 2006, Mr. Martin resigned as party leader and Mr. Graham was appointed interim leader of the Liberal Party. On December 2, 2006, Stéphane Dion was elected leader of the Liberal Party at a leadership convention.

[31] On December 8, 2008, Stéphane Dion announced his intention to step down as Leader of the Liberal Party. On December 10, 2008, Michael Ignatieff was appointed interim leader of the Party.