Families are being asked to take leftover food home

The park at Newnham is a popular city picnic spot with families in the summer.

At night the poolside activity is from colony of rats living just yards from the water.

Mothers in the park with their children said they had been completely unaware of the problem and were unhappy because of the health risk.

Rats are a danger because they carry Weil's disease.

Where they urinate, there is a risk of passing the infection to humans. It can be fatal.

The chlorinated water is checked regularly

A spokesman for Cambridge City Council said the pool was chlorinated and the water tested regularly.

"The pool is very safe. It is actually filtrated," said Ian Ross.

"We have quite a large filtration system on the pool and it is checked regularly every day by engineers and it is fully chlorinated."

The council is taking steps to get rid of the rats.