Almost 20,000 incidents of pest infestation have broken out at hospitals over the past two years, it was revealed today.
Outbreaks have included rats in maternity wards, wasps and fleas in neo-natal units and maggots in patients' slippers.
But the Government dismissed suggestions that the problems were linked to spread of hospital-acquired infections like MRSA and insisted the threat to patient safety was "negligible".
The details - released under the Freedom of Information Act - were obtained by the Tories, who contacted all 171 NHS trusts in England.
Of the 127 which responded, almost all were said to have experienced some problems.
Shadow health secretary Andrew Lansley said: "Labour have said over and over again that they will improve cleanliness in our hospitals but these figures clearly show that they are failing.
"It is difficult for health service estates to maintain a completely pest-free environment but the level and variety of these infections is concerning.
"We need greater transparency in NHS infection control, and publishing data like this is one way in which we can drive up overall hygiene standards."
There were almost 20,000 reports of pest problems, while seven out of 10 trusts said they had called in pest control officers more than 50 times since January 2006.
The figures showed that 80 per cent of NHS Trusts reported problems with ants, 66 per cent with rats and 77 per cent with mice.
Cockroaches were said to have been reported at 59 per cent of trusts, fleas or other biting insects at 65 per cent, and bed bugs at 24 per cent.
A further 6 per cent of trusts reported infestations of maggots. Many of the problems were said to have occurred in clinical areas.
Vanessa Bourne, from The Patients Association, said: "Such findings are truly revolting. How can patients be safe amid bed bugs, fleas and rats?
"Once again safety is just rhetoric and not a reality for patients, particularly the elderly and those with suppressed immunity.
"What about those trusts who ignored this Freedom of Information request and said nothing? If these are the standards of those 'coming clean', what does it say about those who stayed silent?
"These findings reveal what happens when money is taken away from where patients expect to see it spent. If these hospitals were restaurants they would be closed down and out of business. Trust Boards must get a grip and show patients they are serious about their legal responsibility for safety."
Health Minister Ivan Lewis said it was up to NHS Trusts to ensure that hospitals were clean and safe for patients.
But he insisted that, so far, there was little evidence of any threat to patient safety.
"The use of pest control is seen as good, proactive management," he said.
"The Health Care Commission have confirmed that health concerns around pest control have, to date, been negligible.
"The claim that insects spread hospital-acquired infections is entirely unproven. There is no evidence of their carriage of antibiotic-resistant bacteria being a hazard to patients.
"Despite this, we expect hospitals to take continued action to tackle these pest problems."