Men are at risk of being "feminised" by thousands of "gender bending" chemicals that are changing the behaviour of humans and animals, according to a report.

Scientists are warning that manmade pollutants which have escaped into the environment mimic the female sex hormone oestrogen.

The males of species including fish, amphibians, birds, and reptiles have been feminised by exposure to sex hormone disrupting chemicals and have been found to be abnormally making egg yolk protein, normally made by females, according to the report by Chem Trust, environmental group.

The authors claim that the chemicals found in food packaging, cleaning products, plastics, sewage and paint cause genital deformities, reduce sperm count and "feminise" males.

Fish have been specifically affected by the gender changing chemicals. In one study, half the male fish in British lowland rivers had signs of being feminised - as chemicals which block the male hormone androgen had been released- leading to the development of eggs in their testes.

Although the report only looked at the impact of gender bending chemicals on the animal world, its authors say the findings have disturbing implications for human health.

Gywnne Lyons, a former Government advisor on chemical pollution and author of the report, said: "Urgent action is needed to control gender bending chemicals and more resources are needed for monitoring wildlife.

"If wildlife populations crash, it will be too late. Unless enough males contribute to the next generation there is a real threat to animal populations in the long term," she added.

The paper lists the affected species and include, flounder in UK estuaries, cod in the North Sea, cane toads in Florida, peregrine falcons in Spain, and turtles from the Great Lakes in North America.

Some male roaches have changed sex completely after exposure to oestrogen from the Contraceptive pill pouring out of sewage works.