The £50m a year that the government is to spend on routinely deep cleaning hospital wards is being spent to reassure the public rather than as a provenly effective way to tackle hospital acquired infections, Alan Johnson, the health secretary, said yesterday.

Microbiologists warned on the day that Gordon Brown, the prime minister, announced the "deep clean" policy that such routine annual cleans would be ineffective and the medical journal The Lancet has since said they will not affect the risk of infection.