Nests packed with toxic moth caterpillars have been spotted in the area and the public have been warned to steer clear of them.

Oak processionary moth caterpillars, which are covered in hairs that are harmful to humans, have been spotted in nests in Sutton prompting warnings from the Forestry Commission.

Groups of the creatures, which are covered in hairs which cause painful skin rashes and irritate the eyes and throat, have been building nests on the sides of trees in the borough.

The Forestry Commission says anyone who sees the nests, which are made from a silky, web-like substance, should contact them or Sutton Council and should not try to remove them themselves.

Dr Yvonne Doyle, London regional director of Public Health England, said: "The nests can be full of irritating hairs, even after the moths have emerged, and the irritating substance in the hairs can remain active for a long time. The hairs can be blown about by the wind, so it’s important that people and animals do not touch or go near the nests.

"Anyone who experiences an itchy or painful skin rash or a sore throat and irritated eyes after being near oak trees in these areas should consult their GP or NHS 111, who have been given advice about recognising the symptoms and appropriate treatment."

The nests are typically the size of a tennis ball and are usually white when new and discolour to match the bark of the tree over time. They are usually on the trunks or branches of trees but can fall off where they can be found by children and dogs or cats.

Alison Field, South East England Director for the Forestry Commission, said: "The caterpillars are building nests in oak trees in preparation for pupating into adult moths in a few weeks’ time. We encourage anyone who sees them to report them to us or to their local council so that they can be dealt with properly.

"We also advise people against trying to remove the nests themselves, even if they own the oak tree. To be as effective and safe as possible this job needs to be timed just right and done by people with the right training and equipment, and the nests must be disposed of properly."

To report a oak processionary moth nest, visit http://www.forestry.gov.uk/opm or call Sutton Council on 020 8770 5000.