Douglas Fraser's blog: "Brown was desperate to keep the SNP out of power"

Nick Clegg suffered his first major crisis last night as 15 rebels, including Alistair Carmichael, defied his leadership of the LibDems on the key Commons vote on whether or not to hold a referendum on the Lisbon Treaty.

The vote - which was lost - saw Mr Carmichael, the party's Scottish spokesman, side with the Tories for a poll because he feels the difference between the original constitution - on which all three parties pledged a referendum - was not significantly different from the Lisbon Treaty.

Mr Clegg had ordered his 63-strong party to abstain as the LibDem leadership wants a referendum, not on the treaty, but on Britain's membership of the EU.

Before the vote, Mr Carmichael, MP for Orkney and Shetland, along with two front benchers, tendered their resignations.

Mr Clegg said he regretted their loss but noted: "The shadow cabinet cannot operate effectively unless the principle of collective responsibility is maintained."

Mr Carmichael told The Herald: "I got no satisfaction from the situation and I'm sure that's true of my colleagues." He said he would continue to support Mr Clegg.

The portfolios of Scotland and Northern Ireland will be taken on by Berwickshire MP Michael Moore, who is also international development spokesman.

The fallout will run to the weekend when Mr Clegg makes his maiden leadership speech at the party's conference in Liverpool.