Labour MPs closed ranks around the Prime Minister yesterday, angrily rejecting any suggestion that their dispute with him over Iraq would jeopardise his leadership.

Backbenchers crowded into an electrifying meeting of the Parliamentary Labour Party to hear Diana Organ, a quietly spoken, little-known MP who had rebelled over Iraq in last month’s debate, lead the backlash.

The Forest of Dean MP laid into those who want to oust Mr Blair, saying that they did not act in her name or in the name of the overwhelming majority of Labour Party members.

A full Commons debate and vote on the use of military force has been pencilled in for Monday as fears that the Government might struggle to get a majority began to evaporate last night. At yesterday’s PLP meeting, Ms Organ said: “I am outraged that these bitter and self-indulgent people should be using the issue of Iraq to undermine the leader of our party at this time.”

To raucous applause, she accused the group of “parading their consciences” and attempting to confuse their issue of military action in the Gulf with their own agenda.

Describing herself as “not a natural rebel”, she said afterwards that her fury had simply “pressed the right button” with colleagues who were equally incensed at the behaviour of the Socialist Campaign Group, which this week called on Mr Blair to consider his position.

Another half-dozen MPs, who either rebelled against the Government or threatened to if no second UN resolution is secured, also got to their feet to support Ms Organ. They praised Mr Blair for “working like a dog” to try to secure a second resolution and said that it was not a matter of confidence in the leader.

Estimates that the number of Labour MPs prepared to oppose war would swell from 121 — the figure in the rebellion last month — to 200 next week appear to be well wide of the mark. Even anti-war organisers could identify only 40 possible new supporters on the Labour benches yesterday and many of these said yesterday that they would back the Government.

The Times has been able to establish less than 20 Labour MPs who might join a revolt. Heading this list is Clare Short and around five parliamentary private secretaries, who, along with the International Development Secretary, would be expected to quit the Government if war went ahead without a fresh UN resolution.

Although the number of Tories opposing military action is expected to rise from a total of 13 last month, Iain Duncan Smith is likely to impose a three-line whip on his MPs and Mr Blair should be able to rely on at least 120 Conservative votes next week.

However, even after clearing the hurdle of a Commons vote, Mr Blair’s postion could be shaken by more government resignations, with speculation focusing on figures such as Robin Cook, the Leader of the Commons, and Angela Smith, the Northern Ireland Minister.

Others, such as Tessa Jowell, the Culture Secretary, and Alistair Darling, the Transport Secretary, are understood to have “raised concerns” over policy on Iraq at recent Cabinet meetings — not least because of criticism within their constituencies. But no one expects such figures to even consider quitting.

Potential recruits for a revolt from the backbenches include Keith Bradley, Ian Davidson, Barry Sheerman, Graham Stringer, David Borrow, Andrew Mackinlay, Chris Mullin and Eric Martlew.

However, much will depend on what happens at the United Nations in the next 48 hours. Hugh Bayley, a former minister who voted with the Government last month, said that he was unlikely to support military action without a second resolution but could yet be persuaded if a new resolution won a majority in the Security Council and failed only because of a French veto.

Mr Stringer, another ex-minister preparing to join the rebellion, said: “I cannot support the Government if there is no second UN resolution.” But he suggested that Mr Blair had won respect from rebels for his attempts to get UN backing. “People also think Clare Short went too far at the weekend and that has given him a certain amount of sympathy.”

Pressure from constituency parties has played a key part in some MPs’ decisions. Mr Sheerman, chairman of the Commons Education Committee, has seen active members in his Barry constituency dwindle from 200 to around 50 in recent weeks. The rest have informed their MP that he can consider them “missing” while Mr Blair supports American foreign policy.

In the Commons yesterday, Mr Sheerman urged the Prime Minister to do more to restrain President Bush’s “unseemly haste for war”.

Cambridge Labour Party is also vehemently against action and the Anne Campbell, the local MP, is expected to quit as PPS to Patricia Hewitt if war goes ahead without UN backing.

Bridget Prentice, in Lewisham East, Jim Dowd, in Lewisham West, Ann Keen, in Brentford and Isleworth, and Martin Linton, in Battersea, are also under huge pressure from local activists to vote against the Government if there is no second resolution.

Many MPs are concerned that voters’ hostility to military action is evolving into a more general sense of opposition towards the Government even on issues such as next months’ tax rises to pay for increased NHS spending.

One Labour MP and PPS yesterday gave warning of a split between the constituencies and Westminster. “If we’re not careful the party will be so damaged that it will no longer be able to campaign properly in May’s local elections.”

MPs in London and the Home Counties are the most vulnerable to such pressure while those in traditional working class seats report strong support for the Government.

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