Steve Richards: This seething frenzy will only end with Tony Blair's departure from Downing Street

With an excessive zeal, Tony Blair has defined his leadership by taking on the Labour Party. Now significant parts of his party take on Mr Blair. Labour is in turmoil. The seething frenzy can end only with the departure of the Prime Minister. There is no other cathartic event or public declaration from anyone that will do the trick.

This became obvious within minutes of Mr Blair's planned departure date being briefed to The Sun. "Blair will quit on May 31st 2007", the newspaper declared authoritatively on its front page yesterday, the latest attempt from Downing Street to defuse the situation. Immediately a whole new set of questions surfaced. Why next summer and not earlier? Why should ministers and civil servants listen to Mr Blair when they know he will be gone by May? Should a cabinet minister stand against Gordon Brown? Is the timetable in the interests of the post-Blair government, or drawn up with other factors in mind?

If this timetable remains in place, these questions and others would rage for nine months, the longest leadership contest in history, made even more surreal because it would be conducted without any candidates declaring formally. In the meantime, Mr Blair's speeches would be reported solely in terms of whether they were helpful to Mr Brown or another aspiring candidate.

Sometimes they would not be reported at all. On Tuesday, Mr Blair made a substantial speech on social exclusion. He might as well have delivered it on the moon. As matters stand, Labour faces an unofficial leadership contest lasting longer than the deputy leadership battle in 1981, which Labour began slightly ahead in the polls and ended 20 points behind.

I do not expect events to unfold in such a manner. Something has changed at the upper levels of the Labour Party. A sign of a different mood in the Labour party came days ago in the widely dismissive reaction to the most recent interventions of Alan Milburn and Steve Byers, Mr Blair's close allies. On Sunday, Mr Milburn argued that the Labour party had to come up with a range of new policies or else the Conservatives would do so in their policy review. Mr Milburn seemed to suggest Labour's ambitions should be limited to announcing Conservative policies before the Conservative Party. Separately Mr Byers has warned vaguely about the dangers of "turning the clock back".

At every level, from those regarded as Blairite cabinet ministers to Blairite Labour MPs, there was despair at these provocative banalities. Until recently, there was a dutiful respect in some ministerial quarters when Messrs Milburn and Byers went to war.

Mr Blair and his most devoted followers are in a similar position on a much bigger stage to David Owen in the final phase of his career. When the SDP voted to merge with the Liberals in 1987, Dr Owen and a few remaining admirers refused to accept what was happening. Dr Owen decided to lead a "continuing SDP". Late at night he and his entourage would talk about how they alone could save the prospects for a third party. They had charisma. They commanded parts of the media. But the show had moved on. In the end, they spoke for no one but themselves.

In speaking for themselves, some of Mr Blair's supporters defy logic now. On yesterday's Today programme, John Hutton deployed the cliché about the dangers of going back to the past. He was asked whether Gordon Brown would take Labour backwards. Mr Hutton said "no". Privately he probably would say "yes", but if he and others cannot mount a public case, all they do is help the Conservatives in their attempts to portray Mr Brown as "old Labour". They are leaders of the "continuing Tony Blair party", and Mr Blair is not continuing. Yet they have no alternative candidate. They are hovering in mid-air, with no visible signs of support.

Inadvertently, they have contributed to the crisis engulfing their hero. Two separate developments have coincided to produce the current drama. Gordon Brown has concluded that Mr Blair is not interested in what was comically billed as a smooth transition. Instead Mr Brown notes that the likes of Milburn and Byers are on the loose, Labour is slumping in the polls and Mr Blair refuses to map out a timetable that he regards as helpful.

Meanwhile a growing number of previously loyal MPs have concluded separately that this malaise cannot continue for another year. On their own, the disillusioned Brownites and the despairing Blairites would not have been strong enough to achieve their objectives. Together, they make it much harder for Mr Blair to continue, not least because several cabinet ministers have also concluded the game is up.

Before the events of recent weeks, there was one way in which Mr Blair could have remained in Downing Street with relative ease for another few months. If he had endorsed Mr Brown and sought to work with him, a smooth transition might have been possible. In return, Mr Brown might have declared publicly that Mr Blair must be allowed to stay until the agreed departure date.

But Mr Blair seeks to stay on for the opposite reason, to define the future on his terms, locking Mr Brown into his version of New Labour. Mr Brown has no intention of declaring support for Mr Blair's timetable only to find that Prime Ministerial allies use the fresh political space to undermine him further.

As I wrote on Tuesday, the political dynamic is fuelled by irrationality. Mr Blair is planning to go in a few months anyway. I sense that he has come to terms for some time with the fact that that his period in Downing Street is almost up. How much better for Labour if he were allowed to go on his own terms. But Mr Brown and others despaired of what form those final few months would take and whether by the end of it Labour would be in any state to win the next election. This is not irrational. Brown's personal ratings have slumped since the last election. He has been trapped, unable to say very much outside the confines of his brief, while Mr Blair's allies lecture him patronisingly about how only New Labour can win elections.

I concluded in a column in May that it would be better for Mr Blair, the Government and the Labour Party if he went of his own volition in the autumn. I could see it getting only worse for Mr Blair rather than better. I did not envisage it would get as bad as this. How good it would be, not least for Mr Brown, if Mr Blair could still contrive a dignified exit. If he cannot, his allies will be on the warpath for years to come, with possibly calamitous consequences. Still, only his departure will end the current frenzy, even if it unleashes new forms of turbulence in the months to come.

s.richards@independent.co.uk