One issue beyond any other has gripped the Labour Party as politics resumes after the summer break: the question of when Tony Blair will quit as prime minister.

When Labour MPs get together or, as is more likely with Parliament in recess, chat by telephone, it is the matter they most naturally discuss amongst themselves. Indeed, opposition MPs also debate the shelf life of the prime minister with a vigour and fascination almost equal to that of their Labour counterparts – almost. Unquestionably, Mr Blair’s departure is the big issue for Westminster and, therefore, for Whitehall.

Periods of political hiatus have an oddly familiar feel. I was crossing New Palace Yard in the House of Commons and passed a young minister clambering out from his government car, self-important yet strangely irrelevant. I cast my mind back. When did this minister (whom I shall not name) progress from cheerleading backbencher to obscure member of the government? To which department? It hardly mattered. So many reshuffles; so much earnest activity in the lower ranks of government; so little impact.

This sense of earnest junior ministers carrying on as normal while those at the top of the government were convulsed by destructive political forces was very apparent in the final years of John Major’s administration. The governing party despaired and preoccupied itself with contrary prescriptions for how to remedy its malaise. Pretenders to the crown staked out positions. The opposition made hay. Civil servants were embarrassed, bemused and unsettled.

At one stage during the Major years, a cabinet discussion on the design for a new driving licence – a straightforward proposition, one might think – broke up in acrimony and without agreement as rival accounts of which Conservative minister had said what, were rapidly leaked to the press. Tony Blair’s administration is not yet in a similar state of disarray, but its direction of travel is ominous.

On one day alone last week we had a feverish burst of leaking, plotting, counter-briefing and changes of strategy, all triggered by dissatisfaction with Tony Blair’s reluctance to spell out his preferred timetable for his departure. There was the leaking of a near-farcical Downing Street memo proposing that his final months in office be spent being photographed in ‘iconic locations’, before departing ‘with the crowds wanting more’.

Simultaneously came news of one, two and finally three letters to the prime minister circulating among Labour MPs and calling on him to go now, set a timetable for leaving, or confirm publicly himself that he would be gone within a year. Not wishing to be left out of this new epistolary form of political discourse, another group put their names to a rival statement declaring themselves satisfied with the new timetable to have emerged during the melée.

The emergence of such a timetable was the most significant development. Days earlier, the prime minister had sought to quieten the clamour. In a back-to-work interview he gave notice that he did not intend to go beyond his formula of saying he would not fight another general election and would give ample time for his successor to take over.

"I think most of you can look at what I have said and draw conclusions about that," Mr Blair declared. "Now that is all I am going to say." His edifice crumbled in less than a week. First David Miliband gave an interview saying the conventional wisdom that Mr Blair would be gone in 12 months’ time looked right. This was reinforced by Sir Jeremy Beecham, chairman of Labour’s national policy committee, and others.

This atmosphere of turmoil began to take on not the air of John Major’s final days in office, but those of Margaret Thatcher as events threatened to spiral out of control. The resignations of Tom Watson as defence minister and Mark Tami, Ian Lucas, Khalid Mahmood, David Wright, Chris Mole, Wayne David and Iain Wright as parliamentary private secretaries made the prime minister appear at bay. The air grew thick with recriminations as Mr Blair’s supporters complained bitterly of a plot or coup by Gordon Brown’s supporters.

Things were made still worse as accounts emerged of two fractious meetings between the prime minister and chancellor, in which the pair argued furiously about the timing and manner of Mr Blair’s departure plans. Their first, early-morning encounter at Downing Street was effectively suspended to allow tempers to cool, after Mr Brown demanded a more rapid timetable and Mr Blair complained heatedly at the behaviour of the chancellor’s supporters who signed the letter.

To take the heat out of the crisis, Mr Blair was forced to do what he had long resisted, and himself make explicit an 12-month deadline for his departure. Clearly, he was gravely damaged by the savagery of the in-fighting and risks constantly being portrayed as a lame duck, both at home and abroad.

But Gordon Brown was left weakened, too. His role in the turmoil seemed dubious, petulant and destructive. Even the appearance of factionalism alienates voters. A divided Labour Party, poisoned by plotting and accusations of disloyalty, would be a poor political platform for a future leader.