Deputy Prime Minister Nick Clegg has threatened to veto the Government's NHS reforms unless they are substantially improved, as he set out plans to give the Liberal Democrats a "louder voice" in the coalition.
Mr Clegg was attempting to reassert his party's independence after a bruising set of elections in which voters punished the Liberal Democrats for their record in the first year of the coalition.
Labour leader Ed Miliband said the message from Thursday's polls was that Lib Dem supporters want the party to change course, and called on its ministers to jump ship from the coalition and join him in fighting Conservative policies.
And Labour threw down a challenge to the Lib Dems to vote with it on Wednesday on a series of amendments to water down the Government's school reforms.
Despite the Lib Dems' drubbing at the polls - which saw them lose more than 700 English councillors, dwindle to a rump in the Scottish Parliament and miss out on their long-cherished dream of electoral reform - Mr Clegg insisted he would not pull out of the coalition.
Mr Clegg insisted it was not the time for "tit for tat politics in the Government (with) ministers fighting like cats and dogs". And he said there would be no rewriting of the coalition agreement.
But he told BBC1's Andrew Marr Show: "I think all governments evolve and there's a natural evolution in a coalition Government. In the first instance, you have to work together to take lots of difficult early decisions, but of course over time, your separate identities come out more.
"The message I've heard on the doorstep is people want to hear a louder Liberal Democrat voice in Government. It's already very loud inside Government, we've got to make sure that people hear it outside Government."
The Lib Dem leader made clear his first battle will be over Health Secretary Andrew Lansley's plans to hand NHS commissioning power to GPs and increase the scope for private provision within the health service. Unless there are "substantial, significant changes" to Mr Lansley's proposals, he said he will tell Liberal Democrat MPs and peers to vote them down.
Conservative ministers sought to smooth over rifts within the coalition following a referendum campaign which saw exchanges of insults and accusations between Cabinet colleagues. "There's a lot of heat in an election campaign in any democracy. Of course things are said, but we've had the result and now we move on," Chancellor George Osborne told the Andrew Marr Show.