LONDON (AFP) - British Prime Minister David Cameron on Tuesday said he was recalling lawmakers from their holidays to debate a response to alleged chemical weapons attacks in Syria.

Mr Cameron said parliament's lower chamber would be reconvened on Thursday to vote on a government motion to respond to suspected gas attacks near Damascus - which Britain, France and the United States say were carried out by the Syrian regime.

"Speaker agrees my request to recall Parliament on Thurs," Mr Cameron said in a Twitter message.

"There'll be a clear Govt motion & vote on UK response to chemical weapons attacks," he tweeted.

Mr Cameron's spokesman confirmed on Tuesday that Britain's armed forces were drawing up contingency plans for military action in Syria, but that no decision had been made about what action may be taken.

"We are continuing to discuss with our international partners what the right response should be, but, as part of this, we are making contingency plans for the armed forces," a Downing Street spokesman said.

The prime minister has cut short his holiday in Cornwall, southwest England, to return to his Downing Street office to deal with the Syria situation.

He has been meeting with Deputy Prime Minister Nick Clegg, Foreign Secretary William Hague and Defence Minister Philip Hammond.

He is also continuing talks with other world leaders to agree a "proportionate response" to the alleged gas attacks, which are believed to have left hundreds of people dead.

In his latest call, with his Australian counterpart Kevin Rudd, the two "agreed that it was increasingly certain that the (Syrian) regime was responsible for the attack, particularly since the regime had refused to give the UN immediate access to the site, which demonstrated that they had something to hide," a Downing Street spokesman said.

"They reiterated the need for a serious response to this attack from the international community. The world cannot stand idly by in light of such a significant chemical weapons attack," the statement said.

In tense scenes, the House of Commons gave its approval to the invasion of Iraq by a comfortable margin in March 2003 when Mr Tony Blair was prime minister, shortly before airstrikes began.

Mr Jack Straw, who was foreign minister at the time, said on Tuesday that decision had made lawmakers more sceptical about military action.

"There is an instinct in the British House of Commons to support a British prime minister, of whatever party, where he or she is recommending military action," Mr Straw told the BBC.

"But also there is no doubt that the experience of Iraq has raised the bar of scepticism by the British House of Commons on behalf of the British people about whether military action is justified."

In March 2011, the Commons voted 557 to 13 in favour of military action over Libya.

It is the fourth time Mr Cameron has recalled parliament during a recess - previously a rarely-used step. The last time was for a day of tributes to former prime minister Margaret Thatcher, who died in April.

Lawmakers were recalled twice in the summer of 2011: first for a statement on the phone hacking scandal and secondly after several English cities had been rocked by riots.

The last time parliament was recalled before Mr Cameron came to office in 2010 was in April 2002 to mark the death of the queen mother Elizabeth.