Usual parliamentary convention, codified by the Speaker's Conference in 1973, is that such a motion is moved by the Chief Whip of the party to which the former MP belonged.
This can arise because the former MP did not belong to a party: the writ for the by-election arising from the death of Independent Republican Frank Maguire was moved by Jim Molyneaux, leader of the Ulster Unionist Party;[1] and after Bobby Sands died on hunger strike the writ for a second by-election was moved by Dafydd Elis-Thomas of Plaid Cymru.
[2] When all Unionist MPs from Northern Ireland resigned to force by-elections on the Anglo-Irish Agreement, the writs were moved by senior Conservative backbencher Sir Peter Emery.
The Leader of the House of Commons, John Biffen, successfully moved an amendment to provide that the writ would only be issued on 10 May, three months after his death, in accordance with the recommendations of the Speaker's Conference of 1973.
[5] Unnecessary delay was also the explanation given for the decision of the Liberal Democrats to move the writ for the Oldham East and Saddleworth by-election in December 2010,[6] despite the former MP having been from the Labour Party.
[11] When the government fell over the Campbell Case, the Prime Minister obtained a snap dissolution on 9 October, and the by-election did not take place.
(b) It is inexpedient for by-elections to be held in August, or at the time of local elections in April/May, or in the period from mid-December to mid-February before (under present arrangements) a new Register is issued.
The by-election saw the Liberal Party candidate, David Alton gain the seat from Labour (which it had been continuously winning since 1945) whose incumbent MP Arthur Irvine had passed away in December 1978.
The by-election was scheduled following the resignation of incumbent MP and former Home Secretary Roy Jenkins who had been recently appointed as President of the European Commission.
In a shock result, the Conservative candidate Andrew MacKay wrested the seat from Labour which had been continuously winning from there since 1950, achieving a swing of 15.6% and a majority of 1,949 votes.
In the 1979 general election, Terry Davis, the Labour candidate who had been defeated in the by-election emerged as victor by a margin of 1,649 votes and would serve as the MP of the constituency until it was abolished in 1983.
Despite the Labour party winning a narrow majority of 4 seats in the 1964 general election, Patrick Gordon Walker, the then Shadow Foreign Secretary was defeated from the constituency of Smethwick which he had represented since a by-election in 1945.
The campaign in Smethwick was notoriously racist, with the Conservative Party candidate Peter Griffiths using slogans such as "If you want a nigger for a neighbour, vote Liberal or Labour."
A vacancy was created in the safe seat of Leyton represented by Reginald Sorensen since 1935 (and previously from 1929 to 1931) by elevating him to the House of Lords in December 1964.
In a shock result, the Conservative Party candidate Ronald Buxton wrested the seat by Labour by a margin of 205 votes, achieving a swing of 8.7%.
Patrick Gordon-Walker who against contested against Ronald Buxton, now the incumbent MP successfully won the Leyton seat by a healthy margin of 8,646 votes.
The Conservative Party which had originally selected George Younger as its candidate for the by-election, replaced him with Prime Minister Alec Douglas-Home, following his sudden and unexpected ascension to the Premiership.
The Conservative Party candidate Malcolm St Clair filed a petition against the result, and was declared the winner after a court challenge.
The court ruled the election to be invalid as the voters were aware that Benn was legally disqualified from sitting in the House of Commons and hence their votes would be counted as being "thrown away"; thus declaring Malcolm St Clair, the runner-up candidate as the new MP.