TESCO, Britain’s largest supermarket chain, has raised the prices on hundreds of best-selling products — in a week when it boasted that it was slashing prices by £30m.

Figures obtained by The Sunday Times show that Tesco increased prices on more than 150 best-selling items in the week beginning September 6.

Rival retailers who have seen the figures claim that, by raising the prices on the best-selling items, Tesco more than paid for the £30m of advertised price cuts. “It’s a phoney campaign,” said one rival.

But Tesco, which is this week expected to announce that it made a £777m profit in the first six months of the year, dismissed the claim as “nonsense”.

The row comes amid an increasingly bitter war of words between the big supermarket groups.

Last month Tesco complained to the Advertising Standards Authority and Ofcom, the media watchdog, over claims by Asda that it was the cheapest supermarket.

When Tesco announced the £30m price cuts earlier this month, director Tim Mason boasted that the retailer’s pricing was “clear and simple”.

Mason, who is seen as a possible successor to Tesco boss Sir Terry Leahy, said: “By reducing prices by a staggering £5m a week since January, we know we are making a real difference to our customers. Our success is based on doing the best job for customers and is driven by our long-term strategy to lower prices.”

In its press release, Tesco stated that it was cutting the prices of 460 products by as much as 38%. The price-cutting campaign was backed by television and press advertising that promoted Tesco as the country’s lowest-priced supermarket. The campaign was reported to have cost millions of pounds.

However, rivals claim that by cutting the price of low- volume goods and increasing the prices of best-sellers, Tesco in fact benefited by several million pounds.

For example, Tesco raised the price of its four-pack own-brand baked beans from 69p to 78p. Rivals estimate that with Tesco selling more than 13m packs a year, this price rise alone would have saved the company more than £1m.

Other price rises included 6p on a pack of McVitie’s digestive biscuits and 8p on a pack of 80 Tetley teabags — both best-sellers. The largest price increase added 50p to the price of a 24-pack of Carling lager.

A spokesman for Tesco insisted that some of the price rises were on seasonal products, the wholesale price of which had risen, while others were products that had previously been on promotion.

He said: “They are real price cuts. They are long term. And the real judge is customers who are coming back week in, week out and leaving with more money in their pockets because prices are coming down.”

A spokesman for the Consumers’ Association claimed not to be surprised by the revelation that Tesco had raised hundreds of prices while cutting others.

“All supermarket pricing revolves around competition on some products, but not on others,” he said.

The war of words comes at a time of increasing competition between the supermarket chains. Justin King, the newly appointed chief executive of Sainsbury, has attempted to close the pricing gap between Sainsbury and its rivals, while Wm Morrison, the Bradford-based group, has been expanding across the country as it converts the Safeway stores it bought earlier this year for £3 billion.

The revelation of the price rises could damage Tesco’s campaign to force Asda to drop an advertising slogan that claims it is officially Britain’s cheapest supermarket.

The claim is based on the Grocer 33, a weekly basket comparison compiled by the industry’s trade magazine.

The survey is considered by many in the industry to be one of the most authoritative price studies.

All the leading supermarkets employ large pricing departments with responsibility for pricing and for collecting prices from rivals to ensure that they remain competitive. According to one former supermarket chief executive, they also “manage” prices in the run-up to a price-cutting campaign.

Pricing departments are also responsible for producing the headline-grabbing savings figure in an attempt to prove that their price cuts are bigger than those of their rivals.