He will try to get back on to the front foot by fiercely defending his record on the economy, social change and the constitution, and by warning party and union critics that a failure to reform the public services could help the return of a Tory government.

He will do so against the background of a new Populus poll in The Times today, taken over the weekend after the reshuffle muddle and last week’s euro decision, showing that the Conservatives are gaining ground on Labour. The survey put the Tories on 33 per cent, just 4 points behind Labour.

The Conservatives are gaining backing among women and middle-class professionals and managers, it says.

It comes after a Populus poll on Saturday indicated that a third of the public would trust Mr Blair less on other issues because of his handling of Iraq.

The embattled Prime Minister had to agree yesterday to make a special Commons statement tomorrow on the constitutional plans sprung upon an unsuspecting party and Parliament as a surprise element in his Thursday reshuffle.

The Conservatives, scenting blood, failed in an attempt last night to force Mr Blair to the dispatch box today. They announced an emergency Commons debate today on the changes, and said that as Iain Duncan Smith would speak, Mr Blair should reply.

But Mr Blair refused to break a lunch engagement with President Musharraf of Pakistan to take part and said that Peter Hain, the new Commons leader, would speak. That means that the Tory leader will hand over to Eric Forth, the shadow Commons leader.

In an urgent attempt to regain the initiative Mr Blair will restate today the objectives of new Labour, saying that the core of its programme is to “rebuild the public realm” and re-energise the public services. And he will give warning that if changes to the schools and hospitals are not pushed through, one day the Right will return to “demolish the public service ethos”. That would mean more charging, less investment, good service for the wealthy and basic services for the rest, he will claim.

Battered by rows over the lack of consultation over his reforms to the judiciary and setting up a new Constitutional Affairs Department, his alleged preoccupation with international events and the loss of key reforming minister, Alan Milburn, Mr Blair will launch his fightback with a speech attacking Right and Left at a Fabian Society gathering.

It will be a determined effort to switch the spotlight on to his territory and to answer the charge that he has ignored schools, hospitals and transport. He knows that failure to achieve hospital and school reforms would ultimately be far more damaging that the current spat over the constitution.

Mr Blair, hampered by the loss from the Cabinet of reforming ministers such as Mr Milburn, Peter Mandelson, Estelle Morris and Stephen Byers, will take up the mantle of Blairism and reform, reminding his party of the objectives of new Labour and the perils of standing still.

His relaunch will recall memories of his ill-fated speech to the Women’s Insitute in 2000, also seen as a move to revive his Government after the setbacks of the local election results that year.

He will say that the Government and party must press ahead with progressive reform across the public services, and that “the essence of progressive politics is the willingness to fight for change and not defend the status quo”.

Conservatives and their supporters are now on their traditional rightwing agenda — anti-public service investment, anti-European, anticonstitutional change, and ultraconservative on social issues, believing that opportunity for the few will benefit society as a whole, he will say.

The Left must not fall into the trap of responding by “defending the status quo, big state solutions and unreformed public services.” He will say: “Our task is to prepare Britain for the future. In the public services that means combining equity with choice. Equity means everyone being able to get access to good public services, choice means opening up the system.”

In a clear message to critics of the foundation hospital legislation, now to be pushed through by Mr Milburn’s successor, John Reid, Mr Blair will tell the Left that new Labour has shown that it is possible to win an election, deliver progressive change and to win again.

To those resisting change Mr Blair will argue they are defending a system that has entrenched inequality.

Mr Blair will also say that the centre of gravity moved hugely to the Right in the 1980s. It has moved back. “The Centre Left can be confident. We are the party of change and change is the theme of our times.”

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