Jamie's £1bn boost for store

One is the most popular chef of the last decade. The other is one of the greatest footballers of modern times. Now both have been officially named as the most effective advertising frontmen ever - earning hundreds of millions of pounds for the firms that employ them.

According to new research, the £41 million spent by Sainsbury's on campaigns using Oliver generated an extra £1.12 billion of turnover - overall turnover was £17 billion. Oliver was single-handedly responsible for £200 million of Sainsbury's £535 million profits in the past two years.

The same research showed that Match Of The Day anchorman Gary Lineker has sold 112 million packets of Walkers crisps in the same period.

They are extravagant claims - but were not made by the stars or their agents. The figures were revealed by the companies themselves in prize-winning reports for the prestigious advertising effectiveness awards, held by the Institute of Practitioners in Advertising at the London Hilton last night. Sainsbury's admitted it was surprised by just how effective its campaign had been.

Kate Nicholson, head of advertising, said: "Jamie has far exceeded our expectations. It does sound like an awful lot of money but we know he really has generated these extra sales because we have researched it very carefully.

"Jamie has been a crucial part of our turnaround, I don't think anyone else could have done it," she said.

Walkers said that the Gary Lineker campaign was so successful that it had been copied all round the world. "In the last two years the campaign has helped to sell enough crisps to cover the whole of Holland," said a spokesman. "We are signed with Gary for the next five years - another 25 commercials at least."

Oliver is said to be receiving £1 million a year to appear in the Sainsbury's ads.

According to Walkers, who share the UK's largest ad agency, Abbott Mead Vickers BBDO, with Sainsbury's, Lineker is thought to be responsible for sales worth an estimated £60 million. The former footballer has a £1.5 million "golden handcuffs" deal with Walkers preventing him from endorsing any other product until 2006.

A recent survey of 4,000 advertising campaigns found that those using celebrities are up to 10 per cent more effective than those without. But a big name is no guarantee of commercial success. "Celebrity ads only really work if you have the idea and then look for the person who can dramatise it," said Bridget Angear, of Abbott Mead Vickers.

"Sainsbury's was widely thought of like the old Tory party - pompous, arrogant and out of touch. Jamie Oliver is the perfect antidote to that. And Gary Lineker was the ideal interpretation of a nice man turned nasty by the irresistibility of crisps."

However, celebrity campaigns can misfire. More often there is a problem when the celebrity fails to support the product. In 1999 Britney Spears was photographed drinking Coke and not Pepsi, for whom she was a well-paid spokesperson. And in 1997 People for the Ethical Treatment of Animals had to dump Naomi Campbell after she modelled fur for Karl Lagerfeld.