Downing Street has dismissed a report that officials close to Tony Blair are considering putting off a euro referendum until after the next general election.

The Times newspaper says pro-euro people close to Mr Blair support such a move if the government can not state unequivocally that its five economic tests have been met.

The five tests

Flexibility Growth and jobs Impact on the City Convergence Investment

The government's assessment of the five tests for UK euro entry will be judged by June next year at the latest.

Fresh speculation over the timing of the vote came as the German ambassador to the UK said an advert depicting Hitler as a euro supporter would "deeply offend" people across Europe.

Tests doubts

The Times reports that a senior Number 10 official has said a referendum six months after the next general election (widely expected for 2005) was a possibility if the government did not choose to call one in this Parliament.

The No Campaign have won Bob Geldof's backing

The report comes after an academic study earlier this week suggested the economic tests had been met and that it was now essentially a question of having the political will to call a referendum.

But the newspaper suggests there are growing doubts among some pro-euro campaigners that the Treasury could deliver the "clear and unambiguous" yes Mr Brown says are needed before a referendum.

A delay would allow three more years of economic convergence with countries using the euro, as well as for the single currency to prove itself a success.

Opinion polls continue to show a majority of people would vote "no" in a euro poll - and a less than clear verdict on the tests would make turning round that opinion even harder.

Missing the boat?

Rupert Murdoch, owner of the Times, last month said he would use his UK newspapers to spread an anti-euro message ahead of a referendum.

Anti-euro campaigners would want to use a "no" vote to bury the issue for years.

Downing Street said on Thursday that it had "no idea" where the story had come from.

Mr Blair's official spokesman said: "It appears to be crystal ball gazing with a large number of hypotheticals thrown in."

The policy was unchanged, said the spokesman, and nobody at Number 10 was trying to send a "coded message" through the Times.

A decision not hold a vote next Spring would surprise many - the prime minister warned last year that the UK had "missed the boat" in Europe too many times in the past.

Heseltine says political leadership is needed

But there is speculation a delay could suit Mr Brown's widely perceived ambition to succeed Mr Blair as prime minister.

He would be able to expect the prime minister to step down after winning a euro poll, thus having nearly a full term in office before facing the electorate.

Labour strategists might decide that holding a referendum after the next poll could also mean the issue might hamper the Conservative election campaign.

There are divisions on the issue in Labour ranks too, however.

A group of Labour MPs have pressed for there to be no referendum until after the next election, although some of their opposition to euro entry is likely to continue after the poll.

New 'no' drive

Mr Brown is seen as more sceptical than Mr Blair about the euro, yet his full support is seen as essential if the government is to win a "yes" vote.

The euro debate has been back at the forefront of political talk this week after the anti euro campaign this week launched a cinema advertising campaign featuring comedians like Harry Enfield and Vic Reeves, as well as former rock star Bob Geldof.

That advert has sparked attacks for being "tasteless and offensive" because it features Rik Mayall as a spoof Hitler saying: "Euro, yes please."

German ambassador Hans-Friedrich von Ploetz said: "Stereotypes always relate to something in the past, link it to something in the present and ignore the facts."

Many pro-Europeans want the government to press ahead with a referendum - the Britain in Europe group has told BBC News Online it is planning its campaign around a spring vote.