ASDA is stepping up the war against Tesco, Britain’s biggest supermarket group, with an official complaint about a claim made by Goldman Sachs that Tesco is cheaper than its rivals.

The complaint to the Financial Services Authority, the leading City watchdog, comes as rivals fear that Tesco has gained control of almost half the available supermarket development sites in the UK, giving it a key competitive advantage.

Tesco’s increasing stranglehold on sites has triggered complaints from other supermarkets to the Office of Fair Trading.

The complaints to the FSA and the OFT come as Tesco prepares to release half-year results showing that profits are 10 per cent higher than last time, at £885 million. Tesco’s strong figures will be accompanied by plans to create 7,500 jobs between now and February.

In a letter to the FSA seen by The Times, Gordon Maddan, regulatory affairs manager at Asda, says that Goldman Sachs’s note Stock focus on Tesco is misleading. He says: “A number of errors in the price comparisons being made have been identified.

“In our view, Goldman Sachs should withdraw their advice and publish a correction.”

Mark McCullough, food retail analyst for Goldman Sachs, said in the note: “We believe Asda’s extensive internal restructuring programme may have resulted in the new management taking its eye off the ball on pricing, with Tesco successfully exploiting that weakness.”

A spokesman for Asda said: “We think we are the cheapest, and in the past the survey has just confirmed what we already knew. When the last survey showed Tesco to be cheaper, then we had a closer look and found a lot of inaccuracies.”

Goldman Sachs said yesterday: “The research compares a similar basket of goods and we have never received a complaint. We were surprised to be told that Asda has written to the FSA on this subject. They did not contact us.”

The row comes amid fears that Tesco’s proposed sites easily outstrip rivals’ plans. Industry experts believe that Tesco has a total land bank of more than 185 development sites, which, if all of them received planning permission, could create more than 4.5 million sq ft of new supermarket space.

Tesco sites are thought to total more than the combined land banks of Asda and Sainsbury’s. The Competition Commission’s recent report on the Wm Morrison-Safeway merger found that Tesco had about 45 per cent of sites with planning permission.

A spokesman for Tesco admitted that Tesco was snapping up a large number of new sites as part of its drive to expand its non-food sales. “The planning process is an open one and it is well known that we are trying to win space to grow our non-food offer in more towns,” the spokesman said. He added that some of the sites were for extensions to convert some Tesco stores to Tesco Extra, its hypermarket format. Tesco claims that less than a quarter of the population has access to a Tesco Extra store.

“Competition for new sites will inevitably hot up as rivals recover,” the spokesman said. He denied claims that Tesco’s dominance in the land market would help to push up its market share to 45 per cent.

A spokesman for Somerfield, whose chairman, John von Spreckelsen, referred to the OFT this year as the “Office that Favours Tesco”, said that it was concerned that the market was not a level playing field. He said that Somerfield was alarmed by Tesco’s expanding land bank.

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