Geldof's 'No to euro' campaign

Live Aid organiser Bob Geldof today spearheads an array of top stars warning Tony Blair to abandon plans to join the euro.

He becomes the biggest - and most surprising - celebrity name to fight to save the pound in a cinema advertising blitz to be seen by at least five million people this summer.

The big screen campaign, unveiled by the anti-euro No Campaign, is designed to destroy the Prime Minister's repeated jibe that sterling's supporters are an extremist cocktail of little Englanders, Tory Rightwingers and elderly xenophobes.

The Irish singer-songwriter, who earned an honorary knighthood for organising the Live Aid charity concert, is the opposite of that caricature.

He is joined by comedians including Harry Enfield, Vic Reeves, Rik Mayall and John Sessions - all anti-Establishment figures who are hugely popular with Britain's youth.

Katharine Hamnett, who famously wore a T-shirt against the siting of Pershing missiles in Britain during one of Margaret Thatcher's Downing Street receptions, takes part, along with chef Gordon Ramsay. All have appeared for no fee. Such a line-up of stars will be a bitter blow to a Prime Minister who has, until now, prided himself on his talent for wooing youth icons to New Labour.

Mr Blair will know better than most that they present a far more formidable challenge to his hopes of holding a successful referendum on joining the euro than Iain Duncan Smith's Conservatives.

Tellingly, the No Campaign, which has copied New Labour's publicity and polling techniques, has chosen to leave out Tory supporters from the 90-second adverts in a deliberate attempt to distance themselves from the Opposition party. Three Labour MPs, Frank Field, Kate Hoey and Diane Abbott, do take part - and warn that joining the euro could mean less money for public services.

However, it is Geldof who is regarded as the secret weapon of the campaign. The former Boomtown Rats frontman has been involved in a series of campaigns which cut across party politics. As a confirmed philanthropist whose native country is already a member of the eurozone, he is an impossible target for Downing Street to attack.

In the two advertisements, Geldof describes the euro as "hugely undemocratic" and insists: "It's not anti-European to be against the euro. I just have not heard an argument that stacks up for Britain entering the euro."

Both advertisements end with him appealing to people to join the No movement, saying: "I don't believe in the inevitability of the euro for the UK simply because people are free here to say no and be listened to - unlike in Brussels."

Enfield appears as his comic creation Tim Nice-But-Dim - who is the only character to support the single currency, although is unable to think of a single reason why. Reeves poses as a salesman comparing a wad of euro notes with lavatory paper. Mayall pushes bad taste even further by dressing as Adolf Hitler at the Nuremberg rally, bellowing: "Ein Volk! Ein Reich! Ein Euro!"

Downing Street has long assumed that this summer would mark a turning point in the fortunes of the Yes campaign. But the polls show opinion is opposed, with one recent ICM survey showing only 25 per cent support for membership.

Mr Blair is thought to favour a referendum next spring but he will not decide until this autumn after looking at the polls and the Chancellor's five economic tests.