Straw reprimanded for claim that deal on EU blueprint is 'not absolutely necessary'

Tony Blair moved swiftly to distance himself yesterday from claims by Jack Straw, the Foreign Secretary, that agreement on a new European Union constitution was "not absolutely necessary".

In a marked shift from Mr Straw's remarks on Monday, Downing Street made clear that the Prime Minister was not going into next month's Brussels summit expecting failure.

It is understood that No 10 told the Foreign Office that it was a "mistake" for Mr Straw to suggest that an enlarged EU of 25 nations could cope without a new treaty.

The mild reprimand for the Foreign Secretary came as Britain was braced for fresh conflict over plans for the EU blueprint at key negotiations this weekend. Proposals to be tabled by the Italian presidency today are not expected to hold out the hope of progress on the UK's worries over tax harmonisation, defence and foreign affairs.

Mr Straw was revealed by Sky News yesterday to be the "senior Cabinet minister" who had told journalists that "life will go on" even if negotiations on the proposed constitution collapsed. "This is in the category of highly desirable, but it's not in the category of absolutely necessary. If there were no agreement it would complicate all sorts of things, but plainly life will go on under existing treaties," he told a media briefing on Monday. The Foreign Secretary was rewarded with lurid headlines in Eurosceptic newspapers, which declared that Britain was preparing for failure in the talks on the blueprint.

Downing Street accepts the tactical need to signal its determination to stick by its so-called "red lines" on the constitution. These include demands for changes to the text on defence and foreign affairs, and to proposals that could lead to an end of the national veto in limited areas of tax, social security policy and energy policy, as well as the harmonisation of criminal procedural law.

However, Mr Straw's remarks, which came hours before Mr Blair and President Jacques Chirac stressed their hopes for progress on the issue, infuriated senior pro-European figures in the Government. One Downing Street source said: "If yesterday was meant to emphasise we don't take the summit for granted, then fine, we are there. But equally we don't go into it expecting to fail. It is going to be a difficult summit. It is important to underline to the public and our partners our determination that our red lines remain. We believe that will happen. We still believe a deal is possible. We haven't decided that a deal is impossible."

Another Government source was more forthright. "We all know we have to send a shot across their bows, but Jack went nuclear. In doing so, he made us sound like the Tories," he said.

Gordon Brown, the Chancellor, launched his own offensive yesterday in Britain's attempt to convince its EU partners that Tony Blair is not for turning in his opposition to a European constitution that breaches his "red lines".

Asked whether the UK might veto the draft constitution, Mr Brown replied: "I am standing up for British interests, and what is in Britain's interest is in Europe's interest. We need an open, reforming, flexible Europe, changing to meet the global economic realities it faces."

Any of the 15 EU member states, or the 10 countries due to join next year, can veto the constitution.

The Brussels summit, scheduled for 12 and 13 December, should agree the final text of the new constitutional treaty, butobservers have predicted that negotiations could drag into next year.