British Prime Minister David Cameron is to start the countdown to UK military action in Syria by telling Cabinet colleagues he is recommending a House of Commons vote on Wednesday on air strikes against the so-called Islamic State terror group.

The Prime Minister's decision to call a vote comes after Labour MPs were granted a free vote on military action, paving the way for Mr Cameron to secure the "clear majority" he wants.

In a statement at 10 Downing Street, Mr Cameron said he would put his plan to Cabinet at its regular meeting on Tuesday.

Labour leader Jeremy Corbyn had called for the PM to offer MPs a full two days of debate on the floor of the Commons before they decide whether to give the go-ahead to the extension of RAF bombing missions against IS from Iraq into Syria.

Labour said the vote should not be held until next week at the earliest.

Speaking shortly after his return from the climate summit in Paris, Mr Cameron said: "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 that we have carried out against Isil in Iraq to Syria, that we answer the call from our allies and work with them because Isil is a threat to our country and this is the right thing to do."

Mr Cameron 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 Isil in Syria and Iraq".

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

He added: "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 in my view it s the right thing to do this to keep our country safe."

Asked why he had not complied with Mr Corbyn's call for a two-day debate, Mr Cameron said: " We will make sure that we have a very long and full debate on Wednesday and we will take the action necessary to make sure we have, in many ways, the equivalent number of questions we would often have across a two day debate 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."