An invasion of rats as big as cats is causing nightmares for villagers who say they cannot sleep because of scratching noises.
Dead rodents have been found behind curtains, beneath floorboards and in the gardens of homes in Goreside Lane, Cuckfield.
Carol Edwards said she cannot let her young mentally-ill son outside for fear of the rats and the poison that has been put down to kill them.
She said: "You can hear them in the units, under the floor, everywhere.
"It's a nightmare. We haven't had any sleep since we moved in as they just scratch all night."
Neighbours on both sides of Mrs Edwards' home are reporting similar problems.
About six homes by the old Cuckfield Hospital site in Ardingly Road have been forced to put poison down, including one family with a young baby.
The Edwards family moved into their home in March and within a week they could hear the rodents.
Mrs Edwards said: "We thought they were mice but four weeks later we saw our first rat in the garden. They are horrible - huge brown ones, bigger than the cat. And now we're worried she'll get poisoned too."
Downland Housing Association sent exterminators to the area three weeks ago.
They laid traps and trays of poison in an effort to wipe out the rats but the infestation shows no sign of ending.
Mrs Edwards' son Blake, ten, who suffers from Asperger's syndrome, cannot go in the garden because of the poison.
She said: "We found a dead one in the house the other day. We are constantly stressed out as we are not getting any sleep."
Environmental health officers for Mid Sussex District Council have confirmed there is a rat problem. They believe the rodents could be nesting in a culvert on the old hospital site.
A spokesman said: "Getting rid of pests is not an overnight matter. However, we'd recommend people do not feed pests by leaving rubbish and food lying around."
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