DAVID Cameron has boasted that Alex Salmond and the Scottish Nationalists are losing the battle for independence.

In his most confident intervention in the campaign yet, the Prime Minister has urged the SNP to "bring on the referendum".

Mr Cameron made the claim and issued his challenge during Commons question-time after Angus Robertson, the Nationalists' leader at Westminster, urged him to end the UK Government's scaremongering.

He told Mr Cameron: "The Prime Minister's deputy party leader in Scotland is describing the UK Government's scaremongering about independence as 'silly' while one of his key donors in Scotland is describing it as 'puerile' and the leading Conservative commentator says it's 'tripe'. Given the Prime Minister is in charge of Project Fear for the UK Government, will he ditch this silly, puerile tripe?"

Mr Cameron responded by referring to the flow of analysis papers from Whitehall on the potential impact of Scottish independence saying: "If you look at the information that has been produced by this Government on what would happen in terms of Scottish independence it is impartial, extremely powerful and very sensible."

He added: "The fact is the Scottish Nationalists are losing the argument. They're losing the argument on jobs, they're losing the argument on the economy, they're losing the argument on the influence that Scotland would have in the world. I say – bring on the referendum because you are losing the battle."

At first, there was no response from the SNP, but later Mr Robertson responded saying: "The reality is that the No campaign are running scared of their own Project Fear.

"We are confident that next September a majority will vote yes so that Scotland gets the government we vote for every time – instead of incompetent Tory governments, nuclear weapons on the Clyde and the dismantling of the welfare state, which is the cost of voting No."

Meantime, a senior Whitehall source took a less assertive approach than the PM on the referendum campaign, stressing how there was still a long way to go until September 2018 and that there was not a scintilla of complacency within the Coalition.

However, he noted that the polls were showing Mr Cameron was right to say the Yes campaign was losing. He pointed out how the Nationalists had U-turned on their argument that an independent Scotland would have automatic EU membership and, this week, were forced into a corner on their stance on Nato membership.

Another Coalition source added: "The Nats are making it up as they go along and already appear to be running out of steam."