Downing Street is relieved that the haemorrhage from government they had feared has not happened. Robin Cook has left the cabinet, Home Office Minister John Denham has stood down, as has Health Minister Lord Hunt. Five junior ministerial aides also quit.

Clare Short's astonishing U-turn over resigning in precisely the circumstances that have now come to pass has helped Tony Blair. She gets to keep her job despite having branded the prime minister "reckless", and he gets to parade her change of mind in front of other doubters - including, crucially, Labour members, for many of whom Ms Short has been a much-loved figure.

But she has irreversibly damaged her credibility, and the blunt truth is that from this point on she will be taken much less seriously by her allies and critics alike.

Anti-war MPs are quietly pleased they managed to increase their numbers on last month's Iraq debate. Although they had originally hoped for more than 139 Labour MPs on their side, they had also feared that misjudgements by some on their side - most notably hard-left MPs who called for a coup to replace Tony Blair - would scare off other potential rebels.

Ahead of the Tuesday's vote, Tony Blair had spent an hour addressing a private meeting of Labour MPs urging them to support him. The morning after, he spent a similar length of time addressing the Parliamentary Labour Party the morning after the vote. Given the size of the revolt, a conciliatory tone was only appropriate: as well as thanking those MPs who backed him, he stressed that there was no bitterness or rancour towards the rebels.

Robin Cook's electrifying resignation speech on Monday had undoubtedly helped bolster rebels' morale and numbers ahead of the Commons vote. His departure and the clear, sharp reasons he gave for it also served to counteract the wavering and eventual hanging on to her job by Ms Short.

John Prescott's contemptuous response to the loss of a health minister - "I don't know who Lord Hunt is, he is obviously a minister of government ... I'm sorry for my ignorance" - had also played very badly. Backbenchers saw it as a petty and far from fitting way to respond to the departure of a peer who served as a minister for four years in a government of which Mr Prescott is the deputy prime minister.

A whipping operation unlike any previously seen helped minimise what could have been an even greater revolt on Tuesaday. As well as the party whips themselves, Tony Blair, cabinet heavyweights, ministers of all ranks and even the prime minister's wife, Cherie, applied varying degrees of pressure to MPs to support the government line.

"The strong-arm stuff is very heavy indeed, with promises of career enhancement or career destruction, depending on how you intend to vote," reported one MP before the debate.

"Any of us who were ambivalent were assured not to worry about our members and that no pro-war MP will be deselected, even if it means dissolving the local party," said another.

The focus has been on Labour's anti-war rebels but the Conservatives have not been immune to the differences convulsing Tony Blair's party. Fifteen of them voted with anti-war rebels on Tuesday - one up on last month's tally.

Former frontbencher Andrew Lansley pre-announced his intention to vote against his party line, opposition whip John Randall stood down ahead of the debate, while Jonathan Sayeed, John Baron and Humfrey Malins resigned from the front bench on Tuesday.

Having been even stronger than Mr Blair on resorting to military force to disarm Saddam Hussein, Tory leader Ian Duncan Smith has lately more fully acknowledged the differences of opinion in his own ranks. He used his keynote speech to his party's spring conference last weekend to pre-empt criticism from his own frontbench at the lack of UN backing for war.

They came under heavy fire from Labour and the Tories for their anti-war line, but the Liberal Democrats have enjoyed relative internal harmony over Iraq. Their benches in the Commons were among those that rose to join the spontaneous standing ovation at the end of Robin Cook's resignation statement to the House.

Some Lib Dem MPs who want to make the party more appealing to Tory voters had privately voiced concerns that their leader, Charles Kennedy, had painted himself into an anti-war corner from which he would find it difficult to escape once the fighting starts. But their anxiety lessened as opinion surveys throughout the crisis showed the public to be against war.

Mr Kennedy himself, in the knowledge that he speaks for most of the country, has been firm that his party will oppose any attack on Iraq until the first bullet is fired.

The MPs pressing Mr Blair against war have themselves been under intense pressure from party members.

"My activists see Tony Blair about to go to war with an American Republican president they have no respect for and frankly view as an enemy, while Jacques Chirac has suddenly become their new hero," explains one MP.

"You tell me how I'm supposed to get them out canvassing and campaigning."

With local, Scottish and Welsh elections due on 1 May, party managers fear that deeply disenchanted activists will this time not come round to coming out and doing the hard leg-work all parties rely on to mobilise their vote ahead of polling day.

A collapse in membership is also feared. Labour MPs report members leaving in droves over Mr Blair's Iraq policy, and Labour chiefs know only too well that the 1991 Gulf war provoked the largest wave of resignations on a single issue in decades.

The squeeze on MPs is made more painful thanks to parliamentary selections taking place at the same time. Bethnal Green & Bow MP Oona King only narrowly survived facing deselection after affiliated trade union votes rescued her from the wrath of party members over her support for Mr Blair's position.