There has been a 5% increase in rat infestations in the east

But a spokesman for the firm - which supplies water in Norfolk, Suffolk, Essex, Cambridgeshire, Northamptonshire and Bedfordshire - says work is constantly underway to control the problem.

The criticism follows a report by the National Pest Technician's Association (NPTA) which shows brown rat infestations in the eastern region increased by 5% in 2003.

Barrie Sheard, chairman of the NPTA, said Anglian Water needs to do more to keep rat numbers down.

"They are not spending as much money as they used to on sewer treatments," he said.

Brown rat infestation

"They are now working on the basis of treating the sewer when you see the rat."

But Becky Doughty, a spokeswoman for Anglian Water, said the firm was taking the right measures to deal with rat infestations.

"Where we do see an increase that is where we put bait down. We don't want to put poisons into the environment unnecessarily," she said.

"If we put bait down all year round rats can also become immune to it."

Nationally, brown rat infestations rose by 3%, with the largest increase in London where the number rose by 17%.

Mr Sheard blames the increase in rats on the decline in routine sewer surveys across the country and the over-feeding of wild birds.