David Cameron tonight told Tory MPs not to vote with Labour's "terrorist sympathisers" in tomorrow's crunch vote over bombing Isil in Syria.
The Prime Minister made the comment during a meeting with his backbenchers as he tried to tighten up support for extending military action.
MPs are due to vote tomorrow (Wednesday) on whether to allow UK planes to bomb Isil targets in Syria, as well as Iraq.
It is looking increasingly likely that the Conservatives, who have a majority of just 12 in the Commons, will need MPs from other parties to back the plan in order to get it through the Commons.
Labour leader Jeremy Corbyn is opposed to the plan, but has allowed his MPs a free vote on the issue.
This evening, Mr Cameron told a meeting of backbench Tory MPs not to "sit on their hands" and side with Mr Corbyn and others, who he branded "a bunch of terrorist sympathisers".
Labour's Shadow Education Secretary Lucy Powell was furious with the comment, and tweeted: "David Cameron calling those opposed to air strikes 'terrorist sympathisers' is an appalling comment which he should retract immediately."
A Tory backbencher told the Huffington Post UK tonight that many wavering Conservative MPs were won over to the Government’s side following a meeting with four Cabinet ministers, including Defence Secretary Michael Fallon and International Development Secretary Justine Greening.
“The fact that the Defence Secretary did not do that much of the speaking, and it was the others talking about how they supported the action and there would departments, such as development, were also involved in the planning, helped win over a number of waverers,” the source said.
Mr Cameron is facing a fresh headache over his plans to extend operations after the SNP’s Alex Salmond collected 110 cross-party signatures for a wrecking amendment.
The amendment endorsed by Mr Salmond states the case for the UK’s participation in the air campaign has not been made “under current circumstances”.
The former SNP leader claimed “it is possible” that the Government could be defeated, and added: “We will our best to argue the case”
Mr Salmond, who is the the SNP Foreign Affairs spokesman, said: “I get the impression the Prime Minister felt that by exploiting the difficulties of the Labour’s front bench he would dash for the vote, because support starting to drift away from him.
“I think the majority will be less than the Government has been expected, whether we managed to turn the debate around I don’t know.”