Business Secretary Vince Cable - who earlier held open the prospect of a revolt - said a solution had been found to sidestep the opposition's "cynical games".
The Liberal Democrats have averted a potential Commons embarrassment and announced they will not vote with Labour in favour of a mansion tax.
The coalition parties will instead vote for an amendment which recognises the deep differences between them on the proposals for a levy on £2 million-plus properties.
"This amendment allows Liberal Democrats in Parliament to back our long-held policy of the mansion tax. We created it and will continue to champion it," Mr Cable said.
"The amendment also makes it clear that although we are in coalition with the Conservatives, we have different views on the desirability of a mansion tax. The Liberal Democrats will not however support a Labour motion designed exclusively to play cynical party political games."
Labour leader Ed Miliband recently adopted the mansion tax - a long-cherished Lib Dem policy - and challenged Deputy Prime Minister Nick Clegg's party to break ranks.
Faced with a damaging Commons split, the coalition parties instead devised a compromise amendment that will allow them to remain together in the voting lobbies.
It specifically sets out that "the part of the coalition led by the Deputy Prime Minister" advocates a mansion tax while "the party of the coalition led by the Prime Minister does not".
Shadow Treasury minister Chris Leslie said: "It would be astonishing if the Liberal Democrats failed to back a straightforward motion supporting their long-held policy of a mansion tax on properties over £2 million.
"The Liberal Democrats have a simple choice: either they back the policy they set out in their manifesto and which Nick Clegg made the centerpiece of the Eastleigh by-election campaign or they don't. No amount of wriggling or contortion can get them out of that simple choice."