British lawmakers voted against military action in Syria on Thursday in a stunning defeat for Prime Minister David Cameron.

The government was defeated by just 13 votes in the House of Commons in its bid for a "strong humanitarian response" to the alleged use of chemical weapons by the Syrian regime.

British Prime Minister David Cameron told parliament on Thursday that military action against Syria would not be possible if it was met by overwhelming opposition in the U.N. Security Council

Cameron made his case for military action against Syria in the face of strong resistance from the opposition and public skepticism.

Britain would still be permitted under international law to take military action against Syria even if such a move is blocked by the U.N. Security Council, according to legal advice published Thursday.

The government said the advice states that the legal basis for any such action would be "humanitarian intervention" and "if action in the Security Council is blocked, the UK would still be permitted under international law to take exceptional measures".

Britain will not take military action against the Syrian regime before United Nations inspectors report back on evidence of chemical weapons attacks, according to a motion published by the government Wednesday that is set to be put to a parliamentary vote.

Lawmakers are due to vote on Britain's response to the attacks on Thursday but any military action will require a further vote of parliament's House of Commons after the U.N. experts report back, according to the motion.

British Foreign Secretary William Hague said Wednesday that talks at the U.N. over a response to the Syrian crisis would continue "over the coming days", as the British parliament prepares to debate possible military action.

Britain sought backing from the U.N. Security Council on Wednesday, submitting a draft resolution to the five permanent members calling for action to protect Syrian civilians.

Envoys from Britain, China, France, Russia and the United States held talks Wednesday on a British drafted U.N. Security Council resolution that could allow military action in Syria.

The meeting ended without any sign that the 15-nation Security Council could vote any time soon on a resolution condemning the use of chemical weapons in Syria.

Britain is considering a "serious response" to the use of chemical weapons in Syria but is not seeking to topple Syrian President Bashar Assad, Deputy Prime Minister Nick Clegg said on Tuesday.

"What we're considering is a serious response... What we're not considering is regime change, trying to topple the Assad regime," Clegg said, after it was announced parliament is to be recalled from recess for a debate on possible action.

Russian President Vladimir Putin on Monday told British Prime Minister David Cameron that there was no evidence yet that the Syrian regime had used chemical weapons against rebels, Cameron's office said.

During a telephone call between the two leaders, Putin said that "they did not have evidence of whether a chemical weapons attack had taken place or who was responsible," according to a Downing Street spokesman.

British Prime Minister David Cameron is cutting short his holiday to deal with the Syria situation, and will meet shortly with top cabinet ministers, a Downing Street spokesman said Monday.

Cameron, who has been on holiday in Cornwall, southwest England, held a series of phone conversations with other world leaders over the weekend but will be returning to London to continue working on the international response to last week's suspected deadly chemical weapons attack outside Damascus.

British Foreign Secretary William Hague on Sunday said that any evidence of a chemical attack by the Syrian regime may have already been destroyed.

"The fact is that much of the evidence could have been destroyed by that artillery bombardment," he said during a press conference after Damascus gave its green light to a mission by U.N. inspectors.