Industry documents seen by The Sunday Times reveal that Tesco has assembled a land bank of more than 185 development sites across the country, which could create more than 4.5m sq ft of new supermarket space.

One of its biggest retail rivals is understood to have written to John Vickers, chairman of the OFT, drawing attention to the land bank and asking the regulator to intervene. So far it has refused to look at the issue.

Tesco’s land bank dwarfs that of its rivals: even combined, Asda, Sainsbury and Morrison have only 3.7m sq ft of developments in the pipeline.

Tesco is expected to have opened 30 of the 185 new supermarkets by the beginning of next year. A further 56 sites already have planning permission.

As Britain’s largest retailer, Tesco will buck the consumer downturn and announce record interim results this week. City analysts expect the group to reveal pre-tax profits of £943m.

Taylor Nelson Sofres, the market-research group, is also expected to publish its latest market-share figures this week. City analysts predict that the figures will show that Tesco has continued to increase its share.

Tesco now owns 546 supermarkets in Britain and a further 646 smaller convenience stores. The group has a 30.5% of the grocery market. Asda, its nearest rival, has 16.7%.

A Tesco spokesman claimed that the figures were misleading. He said Tesco controlled only 13.5% of the total retail market.

Last month Lee Scott, chief executive of Wal-Mart, the American retail group that owns Asda in Britain, suggested that the government should investigate Tesco’s ever-increasing dominance.

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