Jack Straw has warned that a No vote in France's referendum on the EU constitution would present "a problem for Britain".

The foreign secretary's comments come amid fears that the forthcoming British presidency of the EU will be derailed by the need to address the wrecking of the constitution by No votes.

Straw's remarks reflect a near unanimous belief within the government that Britain will be unable to go ahead with its own referendum next year in the absence of a Yes vote in the May 29 French referendum.

Downing Street confirmed that the referendum might be shelved.

Tony Blair's official spokesman said: "It is a statement of the obvious that the results in France and the Netherlands will influence the context in which other countries debate the matter."

An ICM poll for the Vote No campaign, meanwhile, suggests the public is nearly two to one against the constitution: 54 per cent to 30.