England could have no choice but to bomb Scottish airports in order to defend itself from attack if Scotland became independent, the former Solicitor General for Scotland has warned.

Lord Fraser of Carmyllie said if Scotland was left undefended, the enemies of England could use it as a base from which to launch air raids over the border, The Herald reported.

"If that were to happen what alternative would England have but to come and bomb the hell out of Glasgow airport and Edinburgh airport," he said.

The Tory peer was speaking in Edinburgh on Monday at the launch of a pamphlet examining the prospects of the UK splitting up.

In the document Lord Fraser said he was pleased to see that the SNP did not intend to totally disengage from the British military if it achieved independence.

"I would not wish my beloved Scotland to be a war zone for those with evil intent on the sovereignty of England," he writes.

"That was, however, the risk. If we totally failed to defend ourselves alone or in conjunction with England, we offered up ourselves as the battleground."

The Scot said he could not see which countries would have "evil intentions against England" following the end of the Cold War but cautioned against complacency.

"Like others I missed the import of the Balkan crisis and the worldwide ramifications of 9/11 and would hesitate to gaze into the crystal ball and predict the crises even in the rest of the century. All I would argue is that the 20 th century should have taught us never to let your guard down."

Alex Salmond has indicated that he expects a close degree of military cooperation between an independent Scotland and the UK.

Asked on Tuesday whether Scots currently serving on the British military would have to leave he said they would have a choice.

"People would have a choice, we've undertaken that well inherit the military capability in Scotland and we would sustain that," he told the BBC.

"You don't have to say to somebody 'you must leave the British Army', the British Army currently has people from 23 countries serving in it.

"You'd a have choice, a choice of whether to join the Scottish armed forces or to stay serving in the British armed services."