Prime Minister David Cameron today set out a 36-page plan for extending the UK's campaign of air strikes from Iraq to Syria to target Islamic State (IS) bases in the country.
The British premier urged MPs in the House of Commons to back US-led strikes in the region, saying it was in the UK's "national interest" and itcannot afford to stand aside and let other countries carry the burden.
"If not now, when?" he questioned as part of his statement to the British Parliament today.
"The longer IS is allowed to grow in Syria, the greater the threat it will pose. It is wrong for the United Kingdom to sub-contract its security to other countries, and to expect the aircrews of other nations to carry the burdens and the risks of striking IS in Syria to stop terrorism here in Britain," he said.
Cameron's case was set out in a 36-page memorandum to Parliament's foreign affairs select committee, before he made his Commons statement.
In a written response to the committee published before he addressed MPs, Cameron said, "The threats to our interests and to our people are such that we cannot afford to stand aside and not to act".
"Throughout Britain's history we have been called on time and again to make the hardest of decisions in defence of our citizens and our country. Today one of the greatest threats we face to our security is the threat from IS".
Cameron said he would not call a vote in the Commons on air strikes in Syria until he was sure there was a clear majority in favour of action as defeat would be a "publicity coup" for IS.
He told MPs that Britain must judge whether inaction in Syria carried greater risks than action.
He ruled out deploying British troops on the ground and stressed the government had learnt lessons from the Iraq war.
"There's no part of me that wants to take part in any military action that I don't believe is 100 per cent necessary for our own safety and security. That's what this is about. That bomb in Paris - that could have been London. If they had their way it would be London. I can't stand here and say we're safe from all these threats. We are not," he told MPs.
"I can't stand here either and say that we will remove the threat through the action that we take. But do I stand here with advice behind me that taking action will degrade and reduce that threat over time, absolutely. And I've examined my conscience and that's what it is telling me," he added.
Opposition Labour leader Jeremy Corbyn did not immediately make clear whether he would tell his MPs to back military action in a Commons vote.
The shadow cabinet is meeting to discuss the issue this afternoon. If there is cross-party support, a vote on Syrian air strikes will take place in the House of Commons.
