Tory traditionalists will launch a campaign next month to halt moves for the Conservatives and Liberal Democrats to fight on a joint ticket at the next general election.
Opponents of a "continuing coalition" believe David Cameron is privately encouraging the idea, so they plan to stir up a rebellion among Tory MPs and grassroots members. They accuse a "defeatist" Mr Cameron of planning for another hung parliament and insist that the Tories can win an overall majority at the next general election.
The Independent revealed on Friday that the Cabinet has discussed calls for the Tories to help the Liberal Democrats win the 13 January by-election in Oldham East and Saddleworth, even though the Tories are standing in the three-way marginal seat.
Although Mr Cameron and Nick Clegg have said they expect to fight the next election as separate parties, they have left the door open to some co-operation. One option is for the Tories to stand aside in the 57 seats now held by the Liberal Democrats.
But both leaders must tread carefully. After his bruising battle with his own party over university tuition fees, Mr Clegg is under pressure to drop his strategy of ensuring that the Liberal Democrats "share ownership" of all the Government's decisions, including spending cuts, to show voters they can be trusted with power.
The fightback is being organised by the influential ConservativeHome website. Tim Montgomerie, its editor, said: "The liberal Conservatives who want an ongoing alliance with the Liberal Democrats are arguing publicly and behind the scenes for a continuing arrangement between today's two governing parties. Mainstream Conservatives must also organise and prove that there is a better future for the Conservative Party and the country."
Mr Montgomerie said that tax cuts, a tough approach to crime and opposition to an EU superstate were not "right-wing" ideas. They were supported by "the vast majority of the British people but not by the left-wing majority of the Liberal Democrats".
The Tory rebels want a shake-up of the party machine. "It means a party that isn't dominated by a small group at the centre but is an open party where every member and MP plays a significant role. It means a Conservatism of retail policies, not of abstract ideas," said Mr Montgomerie.
Yesterday a cabinet minister said that the two parties could field joint Coalition candidates in some constituencies at the next general election – even though that would alarm activists in both parties.
MPs including Tim Farron, the Liberal Democrat president, want Mr Clegg to trumpet the party's "wins" inside the Coalition more loudly to show the public it has not lost its identity. But Mr Clegg fears that would merely advertise divisions between the Coalition partners. There were signs yesterday that a change of tack by Mr Clegg would provoke a backlash from the Tories.
John Redwood, the former cabinet minister, said: "One of the things I do not like is the new narrative that Lib Dems have come into Government to bridle the instincts of Conservatives. This entails allowing Lib Dems to claim credit for all the nice things that happen." He said lower tax for the low paid, civil liberties and the "pupil premium" were favoured by the Tories as well.