Britain is aiming to scupper German plans to revive the European constitution in a direct assault on the main project of the EU presidency of Angela Merkel, the German Chancellor.

Such a campaign, if successful, would free Tony Blair’s successor from his promise to hold a referendum on the document.

Mrs Merkel told the European Parliament yesterday that a failure to salvage the constitution after its rejection by French and Dutch voters would be “an historic letdown” and set a target for a new document by the end of 2008.

The British Government is keen to avoid holding a referendum on the constitution, despite Mr Blair’s pledge three years ago to do so. Under the German timetable a referendum would coincide with the next general election and cause problems for Mr Blair’s successor.

Mrs Merkel has announced private consultations over the next few months with the 18 countries that ratified the proposed constitutional treaty and the eight that did not to establish every nation’s demands.

A senior British official told The Times that the Government will argue that the EU is working well within its existing treaties and does not need a constitution nor a fresh round of referendums. The only way to avoid that would be to scrap the idea of a constitution or to present a dramatically slimmed-down treaty that makes technical changes in voting arrangements to reflect Europe’s expansion from 15 to 27 nations.

The British position is at loggerheads with Mrs Merkel’s dream of restoring the bulk of the rejected document, including sections that would create a European foreign minister and end the British veto in home affairs and justice policy.

The British official said: “Europe is not broken. Decisions are being taken every month. Legislation is going through — we have just had one of the most ambitious proposals announced for climate change. So you cannot say Europe’s future hangs on another bout of institutional reform.” The British position was last night complicated when Ségolène Royal, the French Socialist presidential candidate, vowed to hold a referendum on whatever new constitutional treaty emerged from the German process.

If she wins, the next prime minister, likely to be Gordon Brown, will struggle to avoid a referendum, even if he is able to argue that Mr Blair’s 2004 promise to hold one no longer applies.

The British source added: “I do not think it is in Europe’s interests to have another round of referenda. We all know what a shock to the system it was to have the French and Dutch votes. Why would you go back into it? If you lose one or two of these you are straight back into the crisis you have just tried to climb out of.”

William Hague, the Shadow Foreign Secretary, said: “It appears that the Government is saying one thing in the House of Commons and another in Brussels.

“Only yesterday Geoff Hoon [the Europe Minister] reiterated the Government’s commitment to a referendum. Now we learn that it is not so committed.”

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