Andrew Grice: Mr Cook has laid foundations for a Labour revolt

The prospect of a long conflict alarms MPs. Most have held their fire - but how long until others put their heads above the parapet?

The prospect of a war in Iraq lasting months is changing the mood at Westminster. Most anti-war MPs have maintained a respectful radio silence since the fighting began, anxious to avoid doing anything that could undermine British troops in Iraq. But there is rising concern about events on the ground. Many Labour MPs who were persuaded to support a war in the crucial House of Commons vote two weeks ago did so with a heavy heart and, moreover, after being assured by ministers that the conflict would be relatively short.

Although ministers deny saying in public that the war would be over quickly, one Labour MP who backed the Government recalled yesterday: "They certainly pushed that message hard in private. They hoped it would be brief and clean."

It is true that the war is less than two weeks old, but, as Tony Blair admits, it feels much longer because most of us are glued to our televisions round the clock. As MPs gathered in substantial numbers at Westminster yesterday for the first time since Mr Blair's visit to Camp David, there was a mood of concern about President Bush's statement that the war would last "however long it takes".

Glenda Jackson, the Labour MP for Hampstead and Highgate, said: "I do think that we should be asking our Government what it expects the next phase of this war to be. We were told that once our troops got into Iraq, they would be greeted with kisses and flowers. It hasn't happened."

Ministers are now trying to reassure worried MPs that the longer than expected campaign stems from their desire to avoid "carpet bombing" the Iraqis into submission. One minister said: "People should realise that we are targeting the regime, not civilians. That will require patience, but it is the right thing to do."

But MPs remain worried. How will coalition forces "minimise civilian casualties" if they are drawn into street-by-street fighting in Baghdad, they wonder. Current conditions in Basra do not bode well for a siege of the Iraqi capital, they argue. "If we are there for a long time, there has to be some means of ensuring that innocent Iraqi civilians are not going to be starved or dehydrated to death," said Ms Jackson.

MPs also noted that Mr Blair declined to make a Commons statement yesterday on his talks with President Bush. Downing Street says the meeting was never going to have "a menu of decisions and announcements". But MPs smelt a rat; they suspect the Prime Minister did not want to face an hour of questions about the role of the United Nations in post-war Iraq – on which he and President Bush disagree – and the Middle East.

On 14 March, the Bush administration promised to publish the "road-map" that is expected to take Israel and Palestine to peace by the year 2005. But it has still not appeared, and Labour MPs are starting to think it was a cynical pre-war manoeuvre. If they think that, what on earth does the Arab world make of it?

How will the growing fears of MPs about the conduct of the war surface? There will be another Commons debate at some point, but the Government is unlikely to offer a formal vote. Hard-line opponents of war, mostly confined to the 40-strong Campaign Group, might stage a symbolic protest by voting against a technical motion for the House to adjourn. But anti-war MPs admit that there is no prospect, with our military in action, of repeating the record-breaking rebellions of the last two Commons votes on Iraq – by 121 and 139 Labour backbenchers respectively.

"Most of us are keeping our heads down – for the time being, at least," said one organiser of the rebellions. "Everyone is wary about undermining the troops' morale and – whether we like or not-- we have to trust Blair now. We can't become armchair generals." However, that view could change if the war drags on. The prospect of Iraq turning into another Vietnam has already been raised – prematurely, perhaps – by Doug Henderson, the former Armed Forces Minister. After two or three months of war, many more MPs will be ready to put their heads above the parapet.

Robin Cook, the former Leader of the Commons, has at least kickstarted a debate after two weeks in which many MPs have been reluctant to mention the war. It was a pity that Mr Cook's searing criticisms of the campaign were overshadowed by his cack-handed call for British forces to be called home, which he hastily withdrew when Cabinet ministers asked whose side he was on.

The former Foreign Secretary should have realised that his words – "I want our troops home and I want them home before more of them are killed" – would play right into the Government's hands. If he had omitted this sentence from his article in a Sunday newspaper, ministers would have been in trouble. The follow-up stories would instead have focused on his revelation that Cabinet colleagues had told him shortly before he resigned that the war would be finished long before the council elections in May and that Saddam Hussein would be overthrown by his associates. His comments gave the lie to the claims by ministers that they had never hoped for a short, sharp war. Another sign that they had done was Gordon Brown's decision to postpone his Budget until tomorrow week (9 April); it was probably supposed to take place when the war was all over bar the shouting.

Mr Blair, frustrated that the 24-hour media is not portraying what he calls the "big picture" in Iraq, is adamant that all will come right. His officials have dusted down the archives of press briefings held during the Kosovo and Afghanistan campaigns, when remarkably similar questions were raised; the "it-will-all-be-over-in-a-matter-of-days" phase was followed by the "it-will-take-years-and-years" approach. Godric Smith, Mr Blair's official spokesman, said yesterday: "He does not get carried away by the successes we have had [in Iraq]. Nor has he been overwhelmed by the difficulties and problems."

Domestic politics cannot be put on hold for ever. A prolonged war is bound to affect the local authority elections, though exactly how will depend on the state of the conflict in May. The unease on the Labour backbenches may spill over into other issues. Significantly, the Government has postponed the second reading of the Bill creating foundation hospitals. Labour whips fear that, once MPs have lost their political virginity by voting against the Government, they are more liable to do it again. For all the talk about rebuilding the Labour Party when the war is over, many Labour MPs believe that relations between Mr Blair and his party can never be the same again.

The longer than expected war is also causing headaches for the other party leaders. Charles Kennedy, who opposed the war but then changed tack once "our boys" were in action, may want to take a more critical stance if the coalition forces become bogged down and there are large-scale civilian casualties.

Conservative MPs wonder whether Iain Duncan Smith's strong support for Mr Blair will return to haunt him in a prolonged war. "Iain hasn't left himself much wriggle room," said one Tory frontbencher. "He's tried to be more hawkish than Blair. If it goes wrong, he'll have nowhere to go." Mr Blair will be in the same boat.

a.grice@independent.co.uk