Unpublished industry research has highlighted a north-south divide in the appeal of celebrity chef Jamie Oliver.

Contemporary media is virtually saturated with Oliver's image. The so-called Naked Chef appears on his television series, the shelves of all major books shops, and he is currently fronting a high-profile advertising campaign for UK supermarket giant Sainsbury's

A survey has suggested however that 26-year-old Oliver is failing to win over all of Sainsbury's potential punters in the north of the country with his mock-cockney charm.

A senior insider working for Sainsbury's in northern England told the Sunday Times: "He's such a cockney boy and all that 'luvvly jubbly' business is something that just doesn't go down well here.

"I don't think people can understand him and I don't think they like him."

The reflections bear out through internal figures, which have shown that while the grocery market as a whole saw sales rise 8.5% during the three months to 14 October, Sainsbury's sales increased by just 2.8%. In short, Sainsbury's is failing to capitalise on an expanding grocery market in the north of the UK.

Last month, Oliver reportedly said that he felt he had been overexposed by the supermarket group. The official line from Sainsbury's, however, is that its fortunes have been revived by the Naked Chef.