Syria crisis: Nick Clegg rules out fresh Commons vote 2 September 2013 Last updated at 11:00 Deputy Prime Minister Nick Clegg: "I don't think there's any point in us going back to Parliament asking the same question" Nick Clegg has said he cannot "foresee any circumstances" under which MPs could be asked to vote again on action over Syria, after Boris Johnson argued there was "no reason" not to do so. The deputy prime minister insisted the government would not "go back" to the House of Commons on the issue. Earlier, London Mayor Mr Johnson said a new motion could be debated if "better evidence" of chemical attacks emerges. The US has delayed strikes pending the approval of Congress next week. Secretary of State John Kerry now says America has evidence the chemical nerve agent sarin was used in a deadly attack in Damascus last month. UN experts are analysing samples of evidence gathered in Syria to determine whether chemical weapons attacks have taken place on a number of occasions The UK government has rejected newspaper claims chemicals exported from Britain after the uprising in Syria began could have been used in the production of agents such as sarin gas Last week, the government lost a Commons vote on supporting in principle action against Syrian President Bashar al-Assad's government by 13 votes. Thirty-nine Conservative and Liberal Democrat MPs sided with Labour to bring the defeat, with several senior ministers conceding that the question would not be asked again. But Mr Johnson, a Conservative, said a new proposal "inviting British participation" in military action could still be put before UK politicians, He wrote in the Daily Telegraph: "If there is new and better evidence that inculpates Assad, I see no reason why the government should not lay a new motion before Parliament, inviting British participation - and then it is Ed Miliband, not David Cameron, who will face embarrassment. We now have a people carrier's worth of political heavyweights who didn't like the outcome of last week's Commons vote on Syria musing that perhaps parliament could be asked to vote again. Lords Howard and Ashdown clambered on board over the weekend, as did Sir Malcolm Rifkind. Now Boris Johnson has joined them. The essence of their case is to test Labour's argument. Ed Miliband didn't rule out military action in principle, so would he change his mind if the evidence changes? But Labour can say this is irrelevant because the Prime Minister has made it clear the UK won't be involved. Nick Clegg has repeated that the UK will not be involved in military action in response to the use of chemical weapons in Damascus last month. But what would the UK do if there was another chemical weapons attack? The Labour leader has been capering around pretending to have stopped an attack on Syria - when his real position has been more weaselly. If you add the Tories and Blairites together, there is a natural majority for a calibrated and limited response to a grotesque war crime. Some other senior politicians, including former Lib Dem and Conservative leaders Lord Ashdown and Lord Howard - and former Foreign Secretary Sir Malcolm Rifkind - have said the US's own delay could allow the House of Commons to "think again." But, questioned at a press conference in Hammersmith, west London, Mr Clegg said: "We're not going to go back to Parliament with the same question on the same issue, in response to the same atrocity the week before last, because that decision was made by Parliament. We've made it very clear to our international partners that that is our decision now. He also said: "I can't foresee any circumstances when we will go back to Parliament again on the same question on the same issue. We did last Thursday and the answer was very clear. Mr Clegg acknowledged that "entirely different circumstances, of course, might require an entirely different set of decisions" but said he would not be drawn on "hypotheticals." On Sunday shadow defence secretary Jim Murphy said there was "unease about the outcome of the vote." "It's not what I wanted," he wrote on his website. I share the unease that we have gone from a stringent conditions-based approach to any UK military action to an unconditional policy of UK military inaction. Meanwhile, Syrian Deputy Foreign Minister Faisal Mekdad told the BBC that any military action against Syria would amount to "support for al-Qaeda and its affiliates," claiming armed groups backed by America had used chemical weapons - not Syrian troops. On Sunday, Foreign Secretary Hague told the BBC he did not believe new information about the attack would make a difference to the MPs who doubted the government's case. Earlier, Chancellor George Osborne also said that waiting for more evidence would not have made a difference to the MPs' decision. President Obama's surprising decision to ask Congress for approval means that a strike which was thought to be imminent will now not go ahead before 9 September - when Congress reconvenes - at the earliest. President Assad blames opposition forces for the attack on 21 August and says his country will defend itself against any Western "aggression." The opposition Syrian National Coalition called Mr Obama's decision to delay possible military action a "failure of leadership," saying it could "embolden" President Assad's forces