Comment: Another blow for Mr Brown

The move throws the Government's hopes for a renewal of the country's nuclear facilities into disarray and with it a significant element of energy policy. And since British Energy is more than a third owned by the state, the Treasury will lose some £4 billion from the proposed sale.

This is very bad news. And it comes at the end of a week of bad headlines for the Prime Minister. Today, a poll for YouGov suggests that only one in seven voters think he is fit for the job. Tomorrow, David Miliband, the Foreign Secretary, sets off on holiday, but not before writing an article for The Guardian which was universally interpreted by commentators as a bid to succeed Gordon Brown. He can take his vacation secure in the knowledge that his hat is now in the ring.

Two Labour MPs have condemned Mr Miliband for his disloyalty. And while most voters will be baffled and bored by the fuss about an article in which Mr Miliband merely urged Labour MPs to attack the Tories, the febrile atmosphere in the Labour Party means that the episode is seen as immensely damaging.

Mr Brown's confused response did not help. He was first reported to be furious, and on Wednesday his office intimated that the Foreign Secretary was "disloyal" and "immature". By the following day, Downing Street issued a statement in support of Mr Miliband's sentiments and describing the Prime Minister as "relaxed". The truth is, there is something like a shadow leadership contest under way - undeclared and unacknowledged but nonetheless, devastatingly damaging to Mr Brown's standing.

Yet for those who would seek simply to write Mr Brown off, today's poll comes as a reality check. It suggests that David Miliband would be no more successful than Mr Brown in an election. Labour's party rules are weighted against any challenge to an incumbent leader and the alternative is a delegation of ministers who would persuade Mr Brown to go.

In response to this twin threat, Mr Brown has told ministers to keep themselves free in the first week of September - he may hope a Cabinet reshuffle will see off potential challengers. He will also, no doubt, appeal for unity and loyalty.

Still, it's hard to feel much sympathy for Mr Brown. In his time, he plotted ceaselessly to unseat Mr Blair. It is a little rich for him to talk of loyalty now.