RAF airstrikes on Islamic State terrorists in Syria will move a step closer when David Cameron tells Cabinet colleagues on Wednesday that he has enough support from MPs to call a House of Commons vote.

The vote is likely to go ahead on Wednesday after a one day debate, Mr Cameron said at Downing Street.

The move comes after Jeremy Corbyn stepped back from whipping Labour MPs to oppose extending the RAF airstrikes and instead proposed giving them a free vote.

This acknowledged the fears of some senior colleagues that forcing a whipped vote would have seriously split the Shadow Cabinet and sparked resignations.

But it now means Labour divisions will be on full display with Mr Corbyn opening for the party in the Commons debate, strongly opposing airstrikes, and Hilary Benn, the Shadow Foreign Secretary, closing for Labour, supporting them.

The Prime Minister now firmly believes he has the numbers to win a “clear majority”.

A two-hour meeting of the shadow cabinet heard that up to 43 per cent of Labour MPs - almost 100 of the 231-strong parliamentary party - backed airstrikes against 57 per cent - around 132 - who would follow Mr Corbyn into the No lobby.

Philip Hammond, the Foreign Secretary, made clear he was confident there was now a “majority of parliamentarians supporting the action”. A motion is expected to be put down later today.

Both Labour and the SNP demanded that, given the seriousness of the issue, there should be a full two-day debate. Yet the PM is abroad on Thursday.

Last night, Mr Cameron explained he was minded to allow an all-day debate; this would last from after the completion of Prime Minister’s Questions at 12.30pm to late evening, possibly midnight, when the vote will take place.

Westminster insiders believe if the vote is in favour of airstrikes, they could take place within hours of its passage.

After returning from the Paris climate change summit, the PM said he believed there was "growing support across Parliament for the compelling case there is to answer the call from our allies to act against IS in Syria and Iraq".

Confining RAF action to Iraq "makes no sense," he argued, when IS itself did not recognise its border with Syria.

"It is in the national interest, it is the right thing to do, we will be acting with our allies, we will be careful and responsible as we do so, but it’s the right thing to do this to keep our country safe."

Rejecting the two-day debate suggestion, Mr Cameron said the Government would make sure the equivalent number of questions often asked across a two-day debate would be taken in one day.

"I want MPs to be able to have full consideration, to make speeches, to make points, to ask me questions, to examine the Government's case," he said.

In a day of high drama at Westminster, the initial focus was on Mr Corbyn and what he would propose at shadow cabinet. His ally Diane Abbott argued that he should order MPs to oppose airstrikes given this was in line with the majority thinking of party members.

Labour said a 1900 sample of almost 65,000 responses from party members over the weekend showed 75 per cent were opposed to extending airstrikes to Syria.

But senior figures in the party, most notably Tom Watson, the deputy leader, and John McDonnell, the Shadow Chancellor, stressed that on a matter of war and peace MPs should be allowed to vote in accordance with their consciences and the vote, therefore, should be a free one.

Labour HQ claimed the mood of the party and the country was swinging behind opposing airstrikes. Earlier, Labour's two most senior politicians in Scotland said the case for bombing Syria had not been made.

Ian Murray, the Shadow Scottish Secretary, said he did not think airstrikes would have an impact on IS and he explained Scottish Labour leader Kezia Dugdale shared his view.

But as Labour’s position for a free vote was confirmed, Nicola Sturgeon, the First Minister, tweeted: “So a party that says it is anti-airstrikes has just made a vote for airstrikes more likely?! Go figure.”

The meeting of the shadow cabinet was said to have been a heated affair.

One source claimed that Mr Corbyn’s “original plan was for the party position to be anti-bombing, even though Labour MPs would be given a free vote. At that point, Hilary Benn threatened to speak from the backbenches in favour of bombing, so Jeremy had to back down".

A later meeting of the Parliamentary Labour Party, which took place in Committee Room 14 with MPs and peers packed inside, was also heated.

One senior source present said people “let rip” against Mr Corbyn and his handling of the Syria issue.

He said: “Jeremy’s new style of straight-talking honest politics has officially been binned. He has tried bullyboy tactics through Momentum(the new hard-left faction) to get his point across. Everyone has played ball with Jeremy but he has been manipulating things behind the scenes.”

A party grandee said there was a “ferocity” of argument aimed against the party leader.

Margaret Beckett, the former Foreign Secretary, told colleagues: “It is not possible for the party to be united when the leader’s office is seeking to divide us.”

But a Corbyn aide insisted it was only “a small minority” of MPs, who were unwilling to accept his leadership and pointed out the majority of MPs and party members opposed airstrikes and "the rush to war".