The Defence Secretary has attacked "insultingly vague" plans for an independent Scottish defence force.
The Scottish National Party's (SNP) proposals do not stack up or come with enough of a spending commitment, Philip Hammond told an invited audience in Edinburgh.
"Defence and security should be at the heart of this debate about Scotland's future and yet, just over a year before the Scottish people go to the polls, the commitments from those proposing independence remain almost insultingly vague, implausibly long on ambition and incredibly short on detail and the means to deliver them," he said.
"I ask myself why? Might it be that they know that any properly informed and well-reasoned analysis will demonstrate that Scotland is stronger and more secure as an integral part of the UK than it would be alone?
"The reality is that, as part of the UK, Scotland benefits from every pound invested in our collective security."
Ships would not be built in Scotland if voters decided to back independence in the referendum in autumn next year, he said.
Mr Hammond was heavily criticised in Scotland last week when he announced that the number of troops north of the border will increase by about 600, far fewer than the thousands promised in 2011 by his predecessor, Liam Fox.