Bruce Anderson: It is almost impossible for Mr Brown to cling on. And it is almost impossible to replace him

The average Labour MP oscillates between febrility, fantasy, fear and despair

Gordon Brown is finished. As the Prime Minister, he is in office, not in power. As a party leader, he is confronted by insubordination on an unprecedented scale; far worse than anything John Major experienced. As an electoral asset, Mr Brown is toxic waste. Yet it is still likely that he will fight the next election.

There are three reasons for this. First, he has every incentive to hold on to his position. If he went now, he would be a strong candidate for the accolade of "worst Prime Minister since 1900". So we can expect him to fight for more time to obtain a better verdict.

Second, the Labour Party's rules favour incumbents. If Gordon Brown could be assassinated in a fortnight, like Margaret Thatcher, he would have no chance. But a Labour leadership contest would take months. It would be accompanied by a gale of public derision against which the candidates would be barely audible; the worst possible way to prepare for the inevitable early election.

In such circumstances, who would want to lead the Labour Party? It might seem like standing to be Mayor of Berlin in May 1945. The youngsters who aspire to the job would be wise to wait until after the election. If any of them won a blood-soaked contest early next year, the fruits of victory would be an embattled interim leadership plus the right to challenge Mr Brown for the title of least effective Premier of the 21st century.

There is a clear conclusion. It is almost impossible for Mr Brown to cling on. It is also almost impossible to displace him.

Scenarios have been discussed. What about another coronation, in which the party rallies round Alan Johnson or Jack Straw? The new leader would almost certainly be a transitional figure, but without Gordon Brown's negatives, he might have a hope of securing a less crushing defeat than now seems probable. One suspects, however, that the era of coronations is over.

Then there are the "what if?" scenarios. What if Tony Blair were still a Member of Parliament? What if some back bencher – the new member for Sedgefield, say – were to offer to resign his seat if Mr Blair would fight it? One suspects that the era of Tony Blair is also over.

So the average Labour MP oscillates between febrility, fantasy, fear and despair. These are not the easiest troops to lead, and Mr Brown has another problem. He has few friends. He can always rely on little Mr Balls, a man who generally talks up to his name. Ed Balls has one distinction. Apart from Quentin Davies, the Tory defector, he is the only man in the Labour Party with fewer friends than Gordon Brown.

Mr Balls has built a career as Gordon's homunculus. He regards himself as the chosen successor, which is probably true. But successor as what? Tony Blair once said that he would know he had succeeded when the Labour Party came to love Peter Mandelson. At the heights of his power, Mr Blair could not bring about that consummation. In the depths of his impotence, Gordon Brown is unlucky to succeed with Ed Balls. Nor is Mr Balls likely to persuade panicking Labour MPs that they should be loyal to Mr Brown.

Gordon has a further difficulty. He spent 10 years snubbing, bullying and intimidating ministerial colleagues, not least Tony Blair. That just about works, as long as the bully is successful. But once he starts to fail, there are too many people who want to get their own back. In particular, there are a number of Blairites who find it hard to forgive themselves for not trying to prevent the Brown succession and now want to punish the PM for their own weakness in 06-07.

The stories are seeping out from No. 10. The other day, Gordon Brown was convinced that Dominic Grieve, the shadow Home Secretary, had made such a strong attack on 42-day detention as to impugn his commitment to national security. Although Downing Street advisers trawled and Googled, they could not find the quote. Their boss expressed gratitude for their efforts in the way that a sergeant-major would thank a recruit for a speck of dust on his rifle. Mr Brown then stationed himself at a terminal. For the next four hours, he sat there unavailingly, emanating gloom and rage. The non-psychiatric interpretation of his behaviour is termed "the playing politics with national security syndrome".

Shortly afterwards, John Prescott was in No. 10, showing around some children. "What's he doing in this building?" exploded Mr Brown. "Get him out of here." (He surely cannot regard Mr Prescott as a potential leadership challenger – otherwise, things are truly desperate).

Embarrassed aides explained that, you know, Mr Prescott had been Deputy Prime Minister until last year, and what harm could there be in showing kids around? Gordon Brown's response was to shut himself in the Cabinet Room for the next two hours, talking to no-one.

In Jonathan Coe's The Dwarves of Death, the principal character says of an associate: "If he hadn't been so intelligent, I think he would have been one of the stupidest people I ever met in my life." Many Labour MPs, and a fair few Cabinet ministers, would now echo those words to describe their leader. In the summer of 2006, I asked a very senior Blairite whether it could be that Gordon was a little autistic. He gazed at me in horrified disbelief. "What do you mean, a little?"

It is unlikely that Mr Brown's temper will mellow under the gentle stimuli of events. Nor does he seem to have any plans to improve his lot. We learn that in early September, there is to be a reshuffle in which Des Browne will be sacked. Yet Mr Brown ought to think twice before he dispenses with Mr Browne's services.

Des Browne is the only minister of whom it can be asserted without fear of contradiction that he is even worse at his job than Gordon Brown is at his. Jobs: Des Browne has two of them, Secretary of State for Defence, and for Scotland. Those for whom he is responsible have an equal claim to feel insulted as he divides his unworthiness between them. But ratifying his nonexistence by his departure, however desirable, will hardly transform Labour's fortunes.

There is only one course of action which would have the remotest prospect of strengthening Labour's position. Messrs Darling, Johnson, Miliband and Straw ought to meet in the depths of privacy, but accompanied by a couple of wise trade union leaders (though judging by recent television appearances, wise trade unionist may be an oxymoron). They must take a decision; back him or sack him. If it is sack him, the quicker the blood is spilt, the less bad. If it is back him, they should try to enforce that on their colleagues.

But we have discussed the difficulties of blood-letting. Enforcement might be even harder. The probability is that the Labour Party will still be talking about backing or sacking at the new year, as the dwarves dance ever closer to death.