Britain looks poised to join air strikes on Islamic State (IS) group targets in Syria this week after Prime Minister David Cameron announced Monday that a vote would be held in parliament Wednesday.

The announcement came after the main opposition Labour party decided to let its MPs vote with their individual consciences rather than trying to force them to oppose military action, meaning Cameron is set to get the clear majority he wanted.

But Labour was left looking deeply split on the issue after its left-wing leader Jeremy Corbyn confirmed that he would vote against air strikes while a string of other centrist MPs said they would support them.

"I can announce that I will be recommending to Cabinet tomorrow that we hold a debate and a vote in the House of Commons to extend the air strikes," Cameron said in a televised statement.

"We will make sure that we have a very long and full debate on Wednesday."

Cameron has wanted Britain to extend its operations against IS jihadists in Iraq to Syria for months but held back because he would not have been able to gain support from parliament due to Labour opposition.

His previous government suffered one of its most embarrassing defeats in 2013 when it was defeated on a plan to take military action against the regime of President Bashar al-Assad in Syria.

However, in the wake of this month's Paris attacks which killed 130 people, he has made a fresh push for Britain to extend its role in the fight against IS.

In his statement, the prime minister said Britain wanted to "answer the call from our allies and work with them because ISIL (another acronym for IS) is a threat to our country and this is the right thing to do."

Foreign Secretary Philip Hammond said he was now "confident" that most MPs would support air strikes when there was a vote.

- 'Not a shambles' -

Meanwhile, Corbyn faces the toughest challenge of his nearly three-month leadership over the air strikes vote.

His party is split between left-wing MPs, supported by many of the grassroots activists who swept him to power, who oppose the strikes and centrist lawmakers who are in favour.

Monday's shadow cabinet meeting was told that some 43 percent of Labour MPs -- nearly 100 out of 231 -- supported air strikes while 57 percent or 132 would oppose them.

His decision to call a free vote was seen as a way of trying to prevent any resignations from his team over the issue.

But analysts said it risked making him look weak because he could not control his party.

The Stop The War Coalition, which Corbyn helped found and which held a 5,000-strong anti-strikes protest at Downing Street Saturday, said a free vote made war "much more likely".

Corbyn's spokesman said there was "no question" that most of the Labour party was against air strikes.

"I don't think it's a shambles, it's taking account of the fact that there are very significant differences of opinion," he added of the decision to hold a free vote.

In a sign of the splits, Labour sources said that in Wednesday's pre-vote debate, Corbyn would open proceedings speaking against air strikes while his foreign affairs spokesman Hilary Benn would speak in favour.

Another reason the issue is so sensitive for Labour is the legacy of past conflicts such as the Iraq war, which former Labour leader Tony Blair led Britain into in 2003 on evidence that was later hotly disputed.

The conflict, which left a total of 179 British personnel dead, is now deeply unpopular in Britain.

A YouGov opinion poll published last week found that 59 percent approved of Britain joining air strikes in Syria, compared to 20 percent who disapproved and 21 percent who did not know.

Some 127,000 people have also signed a petition to parliament urging a vote against military action in Syria.

Britain has eight Tornado fighter jets and an unconfirmed number of armed and surveillance drones already deployed in the international mission against IS.

But it currently only conducts surveillance and intelligence missions over Syria.

Ghosts of conflicts past hang over UK Labour's Syria split
London (AFP) Nov 30, 2015 - A row in Britain's main opposition Labour party over whether to back air strikes in Syria has deepened splits over Jeremy Corbyn's leadership, while reviving uncomfortable memories of wars in Iraq and Afghanistan.

Prime Minister David Cameron is expected to call a vote in parliament this week on joining the international coalition targeting Islamic State jihadists, but needs support from some Labour MPs to secure a majority.

The problem is that Corbyn -- a left-winger who helped found prominent protest movement Stop The War Coalition -- opposes air strikes, while many of his MPs support the move.

As well as complicating Cameron's calculations on whether he can win the vote, the situation has unleashed a round of very public feuding between pro and anti-Corbyn MPs about whether he is the right man to lead the main opposition party.

It is no coincidence that the row is about military action, the most sensitive issue for Labour since former leader Tony Blair led Britain into supporting the US in Iraq on evidence that was later hotly disputed.

The wars in Iraq and Afghanistan are now deeply unpopular in Britain, which lost over 600 troops.

"The Iraq factor is massive -- it's front and centre" for Labour MPs deciding whether to support action in Syria, according to Victoria Honeyman, an expert on British foreign policy at Leeds University.

"They're worried that they will look like they're following the Blairite approach to war, which is tainted," she added.

This is partly why Cameron spent several hours taking questions from MPs Thursday as he sought to reassure them that military action would be accompanied by a major push to find a diplomatic solution to Syria's four-year civil war.

- 'Trots in the bunker' -

The key question facing Corbyn is whether he will let Labour MPs vote with their consciences or impose a "three-line whip" -- a way to try and force the whole party to vote against air strikes, with consequences for those who do not.

This is expected to be decided at a meeting Monday, which promised to be explosive after he told the BBC on Sunday that he had the ultimate power to decide.

One of his closest allies, finance spokesman John McDonnell, supports a free vote but analysts say offering this could leave Corbyn looking like he cannot control his own party.

The leader himself has already written to Labour MPs saying he cannot support air strikes and emailed Labour supporters urging them to submit their views online, saying Sunday he had received 70,000 responses.

"Labour MPs need to listen to that voice," he said Sunday.

This has sparked fury among some, who accuse him of underhanded tactics by rallying support for his own position instead of waiting for the party to make a collective decision.

"How does Jeremy Corbyn and his small group of tiny Trots in the bunker think they've got the unique view on it all?" senior Labour MP John Spellar fumed on BBC radio Friday.

"If anyone should resign after this incident, it should be Jeremy Corbyn."

Another Labour lawmaker, Paul Flynn, told the BBC there were "terrible divisions" while a third, Fiona Mactaggart, called Corbyn's position "unsustainable".

- Democracy or division -

Key to the row is the fact that Corbyn -- a political outsider and serial rebel before becoming leader -- was elected in September thanks to grassroots left-wing support, but is not widely backed by generally more centrist Labour MPs.

A YouGov/Times poll last week found that 66 percent of those eligible to vote in Labour's leadership election thought he was doing a good job -- more than the figure who voted for him.

However, Labour is well behind the Conservatives in overall opinion polls.

If Corbyn does impose a three-line whip and try to make Labour MPs vote against air strikes, Honeyman predicted that some of his frontbench team could quit.

"If you're a member of the shadow cabinet and you defy a three-line whip, there's an expectation that your resignation will be on the desk in the morning," she said.

While that would be deeply embarrassing for Corbyn, it is not clear it would herald the end of his leadership.

The process for removing a Labour leader is complex and Corbyn has a huge mandate from activists, making any challenge to him problematic.

"I'm not going anywhere," the leader said Sunday.

Supporters insist nothing is wrong -- in public at least.

"On Syria, can everyone calm down. We're all simply working through the issues and coming to final decision. Don't mistake democracy for division," McDonnell wrote on Twitter Friday.