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.
Although focused on the SNP's plans, Mr Hammond also warned people in the rest of the UK that overall defence capabilities could be harmed if Scotland leaves the Union. The system is shared across borders and cannot be broken off like a bar of chocolate, he said. Pilots guarding northern airspace are helped by personnel at a base in Northumberland, Mr Hammond said.
He accused SNP politicians of "juvenile" behaviour for assuming that serving soldiers in the British Army would want to volunteer for the proposed Scottish defence force. The "share" of military assets would not include enough hardware. Scotland could inherit one-and-a-half destroyers, five Chinook helicopters and "under one Red Arrow" among other assets, he said. The SNP argues that it would have 15,000 serving personnel in defence forces and that it would get rid of Trident nuclear weapons. The annual budget for defence and security would be met by about £2.5 billion, according to the party's Westminster leader, Angus Robertson.
Mr Hammond said the UK Government's plan for the future of the armed forces demonstrate a "commitment" to Scotland. "An independent Scotland would have to build its defence credibility and its intelligence reliability from scratch and develop its own bilateral relationships, and the success of these would depend in part on what Scotland can offer in return," he said. "I note the claim made by Angus Robertson that, on independence, Scotland will inherit its treaty obligations. The reality is that it would be the rest of the UK that would inherit Nato membership. An applicant Scotland would need all 28 member nations to decide that it met the requirements to join, taking into account its defence policy, including its intended budget, capabilities, missions and objectives."
In a statement, Mr Robertson, the SNP's defence spokesman, said Mr Hammond should have taken the opportunity to apologise for the slimmed armed forces review and the continued presence of Trident in Scotland. "He came to attack the SNP and Scotland, something he could easily have done from his office in London. And he could have saved the taxpayers a return ticket," he said. "He came to insult Scottish service personnel and demean his office by making jokes about Scottish defence needs. People will make their own judgments about the wisdom of making that kind of speech when the reality is it is his Government that has been part of a massive defence underspend of over £7 billion in Scotland in the last 10 years alone, and has cut the defence footprint in Scotland relentlessly over the years."