Ten of the 12 government-funded 'Portas Pilot' towns have seen a fall in the number of occupied shop units, according to a report.
The towns were awarded a share of the £1.2m High Street Innovation Fund, launched a year ago, as well as government support and access to retail guru Mary Portas following her review of the sector.
But a study by BBC Radio 4's You and Yours has found that in 10 of the 12 towns, more units closed than opened in the past year, with a loss of 95 units in all.
Only two towns showed signs of improvement, with Bedminster and Margate adding units in the past year. In total, about 700 units closed, while fewer than 600 opened, the report said.
Ms Portas told You and Yours: "There is no simple solution to the crisis on our high streets. There are no quick fixes but 400 towns are working on different plans to try and reinvigorate their high street. Let's celebrate their achievements and learn and share ideas. Real change will take time."