Liberal Democrat Scottish Secretary Alistair Carmichael has slammed senior Conservatives' "bitchy" briefings against Alistair Darling.

Mr Carmichael said that he did not know who was responsible for anonymous complaints about the former Labour Chancellor's "comatose" leadership of the anti-independence campaign.

But the former Lib Dem chief whip added that he had his "suspicions". His comments come amid growing disharmony between the two Coalition partners.

Mr Carmichael said that the Tory attacks on Mr Darling were politically motivated.

"You get a bit of bitchiness and point scoring in politics, unfortunately it is part of what happens," he said.

"I'm not worried because I think is unjustified, and because it is unjustified will not get any traction and will soon get forgotten".

He added: "Unfortunately I don't know where (the briefings) are coming from.

"Like everybody else I have my own suspicions ... if anyone is doing it thinking that there are being helpful then they are wrong."