chancellor says the launch of Scotland's Future, the white paper advocating independence, was funded by £800,000 moved from the budget of Scottish Water.

"It's unhealthy that they're able to control so much of Scottish life and they're getting away with it basically. They regard the Scottish government budget as being an extension of their campaign."

In a rare criticism by a politician of an individual civil servant, Darling said, "They're getting away with stuff – we'd have been stopped in our tracks by the civil service. He [Salmond] is very fortunate in his permanent secretary: he's incredibly accommodating." Sir Peter Housden is the permanent secretary to the Scottish government.

But the Better Together leader reserves his most acerbic language for the first minister. Asked if he would be happy to doa TV debate against Salmond, he says: "I will but I don't think he'll do it. Because he's very status-conscious. He regards himself as a head of state. As we say in Scotland, he's got a very good conceit of himself. He's very full of himself."