Saatchi & Saatchi, whose anti-Labour campaign slogans helped sweep Margaret Thatcher's Conservatives to power in 1979, will run the Labour Party's advertising ahead of the next election.

A statement by Labour's election coordinator Douglas Alexander ran on the party's website under a photograph showing Prime Minister Gordon Brown with the banner "Not flash, just Gordon" which had been prepared by the London-based agency.

The slogan can be interpreted as showing up the difference between Mr Brown and his predecessor Tony Blair or Conservative rival David Cameron, while conjuring up images of the 1930s comic book hero Flash Gordon.

"It doesn't strike me as capturing the imagination of the public," said Tim Bell, chairman of Chime Communications and Saatchi's managing director at the time of the Thatcher campaign.

"I interpret this as them trying to find a palatable way to distance themselves from the Blair era," Claire Beale, editor of Campaign magazine, said. "I think it is quite funny and makes it look like Gordon has a sense of humour and principles."

Mr Brown, who holds an opinion poll lead, said last week now was not the right time for an election but declined to rule out calling one before the end of the year. Labour's term can run until 2010. It has been in power since 1997.