Haphazard attempts to tackle rodent infestation are raising the risk of poison-resistant rats spreading disease across the UK, scientists have warned.
Research by Gai Murphy, senior lecturer at Salford University, has found confusion and lack of coordination among the organisations that are responsible for pest control.
She said government inaction could have grave consequences. "Although the risk of disease transmission is fairly small, it will become more significant if we are unable to control the rats," Dr Murphy said.
"Unfortunately, the fundamental need to review the legislation on rat control is likely to remain on the back burner until there is a health tragedy."
Dr Murphy's findings will be presented at an international conference on urban pests in the US on Tuesday.
They will fuel concerns raised by European environmental health officers who met World Health Organisation officials on Saturday to discuss the situation.
Andrew Griffiths, principal policy officer at the Chartered Institute of Environmental Health, was among delegates who agreed to begin a three-year study of pest control and public health.
"Nobody argues with the fact that rats are a bad thing, but we have to show the government the evidence that rat control needs more resources," he said.
Brown rats spread Weil's disease and could be responsible for cases of salmonellosis, listeriosis, toxoplasmosis and Hanta virus.
Dr Murphy gathered data from 250 local authorities in England, Wales and Northern Ireland. Their efforts to deal with the public-health problem posed by rats were often hampered by weak legal powers and poor coordination with other organisations.
Significantly, 35 per cent of local authorities had not been told what control measures were being used in their sewers, which are the responsibility of the privatised water authorities. Furthermore, private pest-control firms rarely shared information with them.
Dr Murphy said this disjointed approach hindered efforts to tackle the problem. As it was, 19 per cent of local authorities reported failed attempts to rid areas of rats.
She feared that the rodents may become resistant to anti-coagulant poisons if their use was not managed properly and coordinated with environmental clean-ups and follow-up surveys.
Cases of resistance have emerged in agriculture, with an untreatable infestation reported on a pig farm in Berkshire.
The urban situation is unknown, but eight local authorities suspect that they may harbour rats that cannot be eliminated by chemicals. Dr Murphy said more research was needed to find out if pockets of resistant rodents already existed.