In a surprise move, Geoff Hoon, the Leader of the House of Commons, said that the manoeuvring against the Chancellor by the so-called Blairite outriders was “deeply unhelpful”, “frustrating in the extreme” and would “do no one any good”.

It emerged that Mr Brown would, after all, front Labour’s local elections launch with Mr Blair on Wednesday. There had been suggestions, denied by Downing Street, that he had been excluded.

Now, after the intervention of Ian McCartney, the Labour Party chairman, Mr Brown will be there in what will obviously be portrayed as a show of unity.

It had been reported that Mr Brown had been axed from the main launch and sent instead to a regional event in West Sussex. In fact, officials said, Mr Brown had requested the switch so that he could be near Gatwick Airport for a trip to the United Nations — which had subsequently been postponed. In the deep mood of suspicion gripping both camps, the Brownites were being blamed for allowing the suggestion to take root that the Chancellor had been excluded.

The intervention of Mr Hoon, one of those ministers closest to Mr Blair, showed the depth of exasperation in the Cabinet over the way attacks on Mr Brown are handing ammunition to the Tories and destabilising the Government with local elections looming.

Mr Blair, who returned from Australia and the Far East on Friday after a trip in which he had fuelled renewed speculation over his leadership, was said to be “horrified” at the hostilities. Labour is expected to confirm today that Mr Brown will appear with Mr Blair on Wednesday.

Mr Hoon is one of several ministers, including John Prescott, who have avoided taking sides in the Blair-Brown battleand who are letting their fury be known at the behaviour of the so-called ultras. While Mr Blair was away two former ministers, Alan Milburn and Stephen Byers, made speeches seen as attacking Mr Brown over his tax policies and pensions. Inevitably, they were accused of a co-ordinated plot.

But it was the briefings from Blairites that Mr Brown had used his Budget to harm Labour’s chances in the local elections — his decision not to repeat the council tax discount to pensioners was cited — that outraged the Cabinet majority and is believed to have prompted Mr Hoon to intervene. A senior Brown ally said: “We agree with John Prescott and others that the briefing by these so-called outriders has got to stop.”

A growing view among close supporters of Mr Brown is that the Prime Minister believed for a short time that the intervention of Jack Dromey, the Labour Treasurer, when he disclosed he knew nothing of the loans received by the party, was inspired by the Chancellor.

Mr Blair is said to have accepted that was not the case, but the Brownites think that the suggestion that the fragile truce between Mr Blair and Mr Brown had broken down was enough for the hardliners to seize their opportunity to launch an all-out battle for the future of Blairism, which would lead to someone other than Mr Brown leading the party.

“That is why we think this has happened. It’s madness. Tony must regain control of these people or we are all finished,” a Brown supporter told The Times yesterday.

Another government adviser in neither camp suggested the “ultras” had gone into action because they feared that poor local election results would lead to further calls for Mr Blair to go. They were trying to pre-empt that by blaming Mr Brown in advance for not helping in the Budget.

The Times understands that there have been no recent discussions between Mr Blair and Mr Brown over how to achieve a smooth transition of power.

The Chancellor, who has been advised by Alastair Campbell and Philip Gould, two trusted Blair advisers, about countering the David Cameron threat, regards the talks as valuable, allies said.

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