MPs have rejected Labour calls for a "mansion tax" on properties worth more than £2m to be introduced before the next general election.

Conservative and Lib Dem MPs joined forces to defeat the move by 63 votes after a Commons debate. The Lib Dems, who support the principle of such a tax, said Labour were simply trying to exploit coalition differences over the issue in an "infantile" move. But Labour accused the Lib Dems of "suppressing their principles".

Labour recently adopted the idea of a mansion tax, first put forward by the Lib Dems in opposition but opposed by the Tories, saying it would pay for the reinstatement of the 10 pence income tax band scrapped by Gordon Brown in 2009. Labour urged the Lib Dems to back it in a Commons vote, but its motion calling for a mansion tax to be introduced at the earliest opportunity to "fund a tax cut for millions of people on middle and low incomes" was defeated by 304 votes to 241. MPs are now voting on an amendment put forward by David Cameron and Nick Clegg in which the two parties state their different positions on the issue but highlight their agreement on other tax matters and their achievements in office.

In Tuesday's debate, Shadow Treasury Minister Chris Leslie, said the mansion tax would narrow what he said was a growing gap between low and middle income workers and the "top 1%", who were set to benefit from an income tax cut while others were "squeezed". Urging Lib Dem MPs to vote with Labour on the issue, he said it was a "real chance to finally vote for something that was actually in their manifesto".

Mr Leslie said it would be "astonishing" if the party did not endorse its own policy and suggested it would demonstrate that they were "suppressing their principles in a bid to cling onto power". John Leech - one of a handful of Lib Dem MPs in the Commons chamber at the start of the debate - asked why Labour had voted against the mansion tax when they were in government. Mr Leslie said circumstances had changed.  

The Lib Dems originally announced the policy at their 2009 party conference but were quickly forced to rethink the threshold for properties that would be covered, raising it from £1m to £2m, amid concerns about the number of people who would be affected. Chancellor George Osborne and other leading Conservatives have long opposed the idea and it has never become coalition policy. However, it remains Lib Dem policy and retains support among activists and MPs. The Lib Dems have said they would show their support for the idea but would not be voting with Labour. Instead, they will back an amendment which states that "the part of the coalition led by the deputy prime minister (Nick Clegg)" advocates the idea, while "the part of the coalition led by the prime minister does not".

Conservatives are also expected to vote for this amendment - which will set out the areas of tax policy that the two parties agree on while not committing the coalition to the idea of a mansion tax before the next general election. Lib Dem minister Don Foster said Labour was "trying to drive a wedge" between the coalition partners in an "infantile" manner and his party would not put the future of the coalition at risk by backing the opposition. "Both parties know where they stand (on the mansion tax) and the public is also clear," he said.