AV referendum: Where parties stand
A referendum on the Westminster voting system is set to be held on 5 May. Voters will be asked whether they want to replace the existing first-past-the-post system used to elect MPs in favour of the alternative vote system. This blog examines where each of the parties stand.
The Conservatives agreed to a referendum being held as part of the coalition deal with the Liberal Democrats.
But most Tory MPs, including Prime Minister David Cameron, are campaigning against any change.
They believe first-past-the-post is a tried and tested system which generally provides stable government and maintains the direct link between an MP and their constituency.
During the 2010 general election campaign, many Tories warned changes to the electoral system could lead to permanent coalitions.
More recently, it has been suggested that some Tory MPs are "relaxed" about the possibility of losing the referendum, thinking it would not damage their chances of winning a majority in future.
But most Conservative activists in the country are thought to be strongly opposed to any change.
Labour leader Ed Miliband is supporting the Yes campaign for changing the electoral system, believing it is fairer than the current situation and good for democracy and accountability.
Other senior figures such as Alan Johnson also support AV, but the party as a whole is divided on the issue, with more than 100 Labour MPs saying they oppose such a change.
Several current shadow cabinet members, including John Healey and Caroline Flint, as well former ministers such as David Blunkett, Lord Prescott and Margaret Beckett, are actively campaigning against AV.
Gordon Brown offered the Lib Dems a referendum on voting reform as part of their own coalition negotiations after May's election.
The party flirted with voting reform as an issue before coming to power in 1997, asking the late Lord Jenkins to head a review into the subject.
But his conclusions in 1998 were largely ignored and critics say Labour only returned to the issue when the party looked set to leave power.
THE LIBERAL DEMOCRATS
The Lib Dems are pushing strongly for a yes vote, having launched their own pro-change "fair votes" campaign at their party conference in September.
The party has long called for an overhaul of the electoral system, saying first-past-the-post does not reflect the will of the people, too many votes simply do not count and smaller parties are penalised.
Under the current system, they argue, Labour won power in 2005 with 35% of the popular vote.
AV is not the party's preferred choice, as it has historically wanted a single transferable vote system. In this system, voters rank candidates in order of preference and more than one MP is elected from each constituency.
But its MPs see AV as fairer than the current system and a step forward.
However, what will happen in the event of the party losing the poll, is unclear. Lib Dem ministers have said this would not threaten the future of the coalition but some backbenchers are less sure.