Pro-euro campaigners have conceded that Downing Street's conflict with the BBC has "derailed" the campaign for the single currency.

Supporters of the single currency admit any referendum will now be delayed - possibly beyond the general election.

They had hoped that the prime minister would gamble on an early poll - with some predictions suggesting a Spring 2004 referendum.

The admission will increase speculation of a dramatic restructuring of the pro-euro campaign.

Critics have accused the pro-euro camp of failing to put in place the infrastructure needed to persuade a sceptical public of the case for membership.

It is thought that Britain in Europe chief Simon Buckby will be removed within weeks.

MPs loyal to the government have conceded that the prime minister will be forced to shelve any plans for an early referendum

The pro-European former minister, George Foulkes, said: "It has been derailed by other things. I am reminded of Macmillan's phrase about 'events dear boy'. We have to accept the reality of that."

Pro-European Tories have also conceded that an early poll is now impossible.

Ian Taylor, the Conservative chairman of the European movement, told the Guardian newspaper: "All attempts to have a [pro-euro] roadshow have been knocked out of the window.

"There has been damage to the standing of the government... which is not the right background for what was always going to be a very challenging campaign."

Foulkes added that it "is more important to get the right result" rather than rush into a referendum.