THE Home Secretary raised the spectre of Border posts and passport controls at Berwick and Gretna, and a heightened risk of terrorism, in her speech to Scottish Conservative conference.

Theresa May pleased conference representatives with an attack on the Liberal Democrats and praise for the work of Tories such as David Mundell, Annabel Goldie and the late David McLetchie.

But her main line of attack was on the consequences of a Yes vote in September, which she said threatened "practical co-operation in the fight against crime, an immigration system which works in our national interest, the freedom to move around these beautiful islands without let or hindrance and the citizenship of generations who are yet unborn".

Mrs May said that if Alex Salmond went cap in hand to gain readmission to the EU, he would be forced to sign up to the Schengen Agreement.

"The UK's position on the Schengen Area isn't about to change. So if Scotland had to join Schengen, it would have to construct border checks for a Schengen Area that ended at Berwick or Gretna Green.

"Unlike Alex Salmond, I'm not going to deal in bluster and ropey assumptions.

"A separate Scotland could certainly try to negotiate a Schengen opt-out. But that would have to be negotiated and agreed with all the 28 existing Member States - it is not in Alex Salmond's gift.

"And even if he managed to do that - convincing countries like Spain - it would come at a price. Because in the world of EU negotiations, nothing comes for free. So what would Mr Salmond give up to try and secure a Schengen opt-out? Scottish fishing grounds? A bigger contribution to the EU budget?"