Commons set for crucial boundary change vote 29 January 2013 Last updated at 01:40 MPs are to vote on changes to their constituency boundaries and whether a planned shake-up should be introduced in time for the next general election. The government was defeated earlier this month when peers called for the review currently taking place to be postponed until 2018 at the earliest. Lib Dem MPs are expected to reject Tory calls for this to be reconsidered. The two parties have been in dispute since proposed elections to the House of Lords were dropped last year. The issue has been one of the biggest flashpoints between Prime Minister David Cameron and his deputy Nick Clegg since the two entered government together. Parliament agreed in principle in 2011 to reduce the number of MPs by 50 to 600 and to redraw the electoral map to make all constituencies roughly the same size in terms of number of voters. Some believe the proposals, which were backed at the time by both coalition parties, would help the Conservatives win up to 20 extra seats at a future election. The proposed changes But a furious row over plans to reform the Lords - abandoned in the face of Conservative opposition - have since led the Lib Dems to say they will block implementation of the boundary review until after the next election, scheduled for 2015. Mr Clegg has argued the proposals on the make-up of the Commons and the Lords were part of the same package of constitutional reforms put forward by the coalition in 2010 and accused Conservative backbenchers of not honouring the initial agreement. But Conservative MPs insist that progress on the two issues was not linked and believe that Lib Dem ministers in the government should now vote in favour of the boundary proposals or step down. When MPs consider the matter on Tuesday, Conservative MPs will look to overturn amendments to the Electoral Registration and Administration Bill effectively putting the whole process on hold. But Labour, who argue the boundary shake-up is flawed, are expected to join forces with the Lib Dems to oppose this.