Former Two Fat Ladies star Dickson Wright, attacked Oliver at the launch of BBC2's autumn schedule - both cooks have up-coming series on the channel.
All is not as it seems in the world of celebrity endorsement. Top television cook of the moment and the new face of Sainsbury's, Jamie Oliver, has been outed as a supermarket snob.
Oliver, aka the Naked Chef, was shamed into admitting his distaste for supermarket produce by fellow celebrity chef, Clarissa Dickson Wright, according to The Times.
Former Two Fat Ladies star Dickson Wright, attacked Oliver at the launch of BBC2's autumn schedule - both cooks have up-coming series on the channel.
Oliver admitted he did not use Sainsbury's food at his restaurant Monte, in Knightsbridge, London.
"For any chef, supermarkets are like a factory. I buy from specialist growers, organic suppliers and farmers," he said.
At the same time, championship-winning golfer Tiger Woods was falling into a similar trap in his native United States. The 24-year-old has been forced to admit he does not use the Nike Tour Accuracy brand of gold ball, for which he is paid almost £700,000 a year to endorse.
Hair today
Even Aston Villa star David Ginola, whose bronzed flowing locks have featured in TV adverts for L'Oreal hair products, has owned up to a dark secret - he dyes his hair, which is naturally grey.
What are we to think when household names cash in on their celebrity, but forego their sincerity?
Statistically, these "exposés" are inevitable. Ron Mowlam, whose Celebrity Group acts as a broker between advertisers and famous names, says more than half of all TV and radio adverts have some celebrity input.
"An actor can be paid to say anything but a celebrity has got so much to lose if they don't believe what they're saying," says Mr Mowlam.
He is surprised by the Jamie Oliver's admission, since industry rules have been tightened in an effort to prevent such a embarrassments.
"Regulators now state that if a celebrity is involved in an endorsement there has to be something on record, something they have signed, to say they use it."
Sipping pretty
Former advertising director, Graham Singleton, is less taken aback. He recalls working on a series of Guinness adverts with the Hollywood actor Rutger Hauer, some years ago.
The campaign was discredited when hard-man Hauer let slip that in real life he wasn't a stout drinker. In fact he wasn't a drinker at all, having been teetotal for many years.
In most cases, belief in the product is second to the serious cash sums on offer.
Jack Dee is alleged to have received £750,000 for promoting John Smith's bitter; Oliver is said to have a £1m deal with Sainsbury's; while Madonna, says Mr Singleton, "will not get out of bed for anything less than $5m to $7m".
Some actors eschew the idea of big name endorsement. Oliver's accuser, Clarissa Dickson Wright, says she has turned down a six-figure sum to promote Tesco. Michael Caine is another who refuses all offers, says Mr Mowlam.
Product placement
Others though are simply selective about where their endorsements appear.
"Hollywood celebrities will not do adverts on their home patch because a lot of television and film people frown on the whole advertising industry.
"After the States, the UK is next place they are reluctant to appear, then mainland Europe," says Mr Singleton.
Japan, though, is something of a free-for-all. "The cultural walls are so strong that they can safely advertise things there - and often it will be really crappy products - and it will not rebound on them."
In 1990s Japan, Arnold Schwarzenegger advertised Cup Ramen, an equivalent of Pot Noodle; Sylvester Stallone endorsed ham and Robert De Niro broke a self-imposed ban on endorsements to help promote light bulbs.
Ad break
But while the money is hard to turn down, too much endorsing can lead to over-exposure.
"We have clients now saying: 'Anyone but Carol Vorderman or Joanna Lumley'. They really have been over-exposed," says Mr Mowlam.
Sometimes the decision to endorse is a sign of a celebrity trying to reap rewards in the run up to retirement, says Mr Singleton. For example, Burt Reynolds's part in adverts for Dollond and Aitchison.
"Appearing in an opticians' ad would have been unthinkable for him 10 or 15 years ago. They just milk it at the end of their careers."
Retirement is not something that 25-year-old Jamie Oliver will be contemplating for many years. So should he be worried that disparaging remarks will damage his earning power?
Not at all, says Mr Singleton, who thinks it fits nicely with his cheeky chappie persona.
"With him people will say: 'Well done mate, you've got the money'."