Leading article: A perfect storm facing Mr Brown in Scotland

It's understandable that Wendy Alexander should feel bitter over the way she has been forced to stand down as the leader of Scottish Labour. The £950 donation to her election campaign that she failed to report to Holyrood's standards committee pales when set against the £60,000 that the two Tory MPs, Sir Nicholas and Lady Winterton, claimed on expenses, let alone the gargantuan sums that some Tory MEPs have milked from public funds. It is not as if this money went to her directly.

But gone she has, and her fall echoes a wider collapse in the Labour Party's fortunes and points to more trouble ahead for Gordon Brown. It is a sign of the Prime Minister's weakness that he seems likely to stay out of the fight to succeed Ms Alexander. Once the unquestioned master of the Labour stage in Scotland, his blessing is now seen as counterproductive.

This, then, could be a truly terrible summer for Mr Brown north of the border. There is every likelihood that the battle to succeed Ms Alexander will be bloody and divisive for Scottish Labour, as the competing candidates are forced to revisit Ms Alexander's controversial and probably unwise decision to endorse a referendum on independence.

Meanwhile, the decision by David Marshall to resign as an MP on health grounds exposes the party to the danger of a humiliating by-election result in Scotland.

This will not be an exact repeat of the debacle in Henley, for sure; Labour won Glasgow East by a majority of more than 13,000 in the last election. But even that thumping margin seems no guarantee of holding the seat today, given the electorate's feverish, vengeful mood. With Alex Salmond's Nationalists on a roll, it's not inconceivable that the SNP could take Mr Brown's scalp in Glasgow. Even if they fail but come close to winning, Mr Brown's loss of prestige north of the border will still look fatal.

This will have an impact on his fortunes in England, too. Far more than his predecessor, Tony Blair, Mr Brown is seen as a distinctively Scottish figure. With Labour there in visible disarray and no longer under his effective control, he starts to look like a man with no power base anywhere.

Mr Brown's enemies should not smile too broadly over his discomfort in Scotland, however. A messy succession battle for the Scottish Labour leadership on top of a dire by-election result in Glasgow could start to shake the very foundations of the union itself, hastening the day when Mr Salmond feels bold enough to go for a referendum on independence that he feels he might win.