Labour's former shadow defence secretary Jim Murphy has spoken of his "regret" at voting against air strikes on Syria in 2013 after dictator Bashar Assad used chemical weapons on his own people.

Mr Murphy said he now believes he should have quit his frontbench job rather than follow then leader Ed Miliband into the No voting lobby.

Prime Minister David Cameron was blocked from joining the US in launching air strikes against the Assad regime when 30 Tory rebels and nine Liberal Democrats joined Labour to defeat him in one of the most dramatic Commons votes of the coalition years.

"I should have stood down from the shadow cabinet in the hours before the vote," Mr Murphy told the New Statesman. "Of the hundreds of votes over 18 years in Parliament, 29 August 2013 was the one occasion I allowed commitment to my party to defeat my sense of right and wrong. I should have been true to myself. I will always regret not being so."

Mr Murphy - who lost his seat in May's general election - said that the action being proposed by the Government was "millions of miles" from the regime change alleged by critics and insisted it was not the case that the Commons vote indicated MPs' opposition to any use of force.

Labour had not expected to win its motion, he said. And the party had earlier tabled a proposal for UK military action under certain conditions which won 220 votes, meaning that a majority of MPs had voted for the use of force in one form or another.

"Labour voted against the Government while not expecting to win. The Government voted against Labour while not expecting to lose," said Mr Murphy.

"That night I didn't join in the customary cheers of some opposition MPs that greeted the Government's defeat. How could I? We hadn't just won a vote to protect family tax credits.

"Assad had dropped chemical weapons on schoolchildren in their playground. Parliament had contrived to do nothing about it."