A three-year study claiming large supermarkets have a largely positive impact on market towns has failed to look at the bigger picture, the ACS has claimed.

The study, commissioned by Tesco but conducted independently by the University of Southampton, is claimed to be an update of the research carried out in 1998 by the then Department of the Environment, Transport and the Regions.

But ACS chief executive James Lowman claimed it did not update the study. "That report looked at the impact of out-of-town and in-town supermarkets" he said. "Although the author of the latest report has pointed out positive outcomes for in-town developments, he hasn't questioned the negatives of out-of-town developments."

The study gathered evidence from 8,000 consumers and 1,000 traders in market towns. Researchers conducted 'before' and 'after' surveys in six towns where supermarkets had opened. They found that supermarkets in town centre or edge-of-town locations encouraged fewer residents to leave the town to do their shopping. There was also an added benefit of more people travelling to towns, with a significant 'spill over' of shoppers visiting other independent stores on their trips.

"This research confirms that supermarket ­developments benefit not only ­customers but the wider community," said Tesco corporate and legal affairs director Lucy ­Neville-Rolfe.