In a speech to the North Atlantic Assembly in Edinburgh, Mr Blair continued his attack of the past 24 hours on the SNP.

He condemned the nationalists' policy of phased withdrawal from NATO as simply crazy, saying other countries were queuing up to join the organisation. The nationalists were the only party in any member country seeking to leave, Mr Blair told the audience.

"The SNP - seeking to retreat into isolation - utter folly," he said.

He accused the party of wanting to pull the armed forces apart.

And he criticised their plans for scrapping the nuclear deterrent, "whatever the cost to bases and thousands of Scottish jobs.

"To replace the NATO collective defence policy with one in which Scotland is isolated and on its own, is not just a wholly irresponsible policy for defending the country, but the financial costs, and so the taxes and threat to prosperity, would be enormous," Mr Blair said.

The prime minister also called for a debate on defence policy. "Membership of NATO, a stronger Scotland because of a stronger UK, or separatism in defence? Stronger and safer together? Or weaker apart?" he asked.

He called for a EU decision-making command structure, to be able to act rapidly and without the US and to take strategic decisions on Europe-only operations.

"A stronger, more effective Europe in foreign policy and security will benefit our north Atlantic allies," he said.