Tossing aside his home and foreign secretaries and depriving the deputy prime minister of most of his powers make Blair look desperate. To lose two home secretaries in 16 months is extremely debilitating. To sack Charles Clarke a few days after claiming that he was the right man to sort out the Home Office robs Blair of credibility.

Twelve days ago Blair missed the chance to fire Clarke for incompetence over the release of foreign prisoners. Dismissing him now shows that he is susceptible to media pressure and that augurs badly for ministers involved in crises.

There is a hint that Blair has behaved peevishly. He was angered by Clarke’s delay in briefing him about the prisoner problem and it is disputed whether Clarke really offered to resign — as he claimed — when he first informed Blair.

By dismissing Clarke and demoting John Prescott, Blair seeks to imply that the local election results were caused by the dreadful headlines of recent days. But many in the Labour party think that Blair bears responsibility for Thursday’s savaging at the polls because of the disasters that bear his imprint, from Iraq to the loans for peerages scandal.

The wrecking of Clarke’s career makes an interesting case study. He won almost universal praise as education secretary, his first cabinet job. But after his promotion to the Home Office he never looked entirely happy. He was under intense pressure from Blair to take additional powers to detain terrorist suspects and to create new offences, such as the glorification of terrorism.

Much more than David Blunkett before him, Clarke took seriously the arguments of civil libertarians. Even if physically he resembled a round peg, Blair was clearly bashing him into a square hole. Early in Clarke’s tenure it was already rumoured that Blair was dissatisfied.

Possibly the home secretary’s unhappiness led to a kind of mental paralysis. For example, during April when he knew that violent foreign prisoners had been erroneously returned to the community, why did he not ask the police to trace them, so that when the scandal broke he could point to action taken? Whatever his mental turmoil, Clarke expressed loyalty to Blair in his dignified resignation statement to the media. The prime minister is weakened by the loss of an ally who, despite everything, remains a serious figure.

Jack Straw has suffered a massive demotion on leaving the Foreign Office to become leader of the Commons. He does not have a huge following in the Labour party but his dismissal will arouse sympathy. In no way could he be blamed for the government’s recent woes or its bad election results.

Labour backbenchers know that Straw was doubtful about the legality of invading Iraq without a specific United Nations mandate. Straw had firmly ruled out military action against Iran, while Blair was conspicuously less categorical. Labour MPs will suspect Blair of punishing him for his independence, maybe on the orders of Washington. Worse, some will deduce that Blair foresees an attack on Iran.

Blair’s reshuffle invites comparison with the July 1962 “night of the long knives” when Harold Macmillan sacked seven members of his cabinet, including the chancellor of the exchequer and the lord chancellor. Fifteen months later Macmillan was gone and in 1964 the Tory government was defeated by Labour.

It is still impossible to predict when Blair will leave Downing Street. But the reshuffle has not added to his authority nor strengthened the government. It does not encourage loyalty or affection even among the Blairites. The guillotine has been operated by a condemned man. His opponents inside the party openly say that a reshuffle is no help because Blair is the problem.

But, unlike in the Macmillan case, the demise of the prime minister will not be followed quickly by the end of the administration. Labour may be doomed but its death agonies will stretch out over many years.

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