Common pesticides dramatically increase the risk of Parkinson's disease, research has revealed.

A study of chemicals in everyday products such as weedkillers and fly sprays found users were almost twice as likely to develop the brain condition.

Only last week it was revealed that much of the fruit and vegetables we eat — including free fruit given out in schools — is tainted by pesticides.

There are 120,000 Parkinson's patients in Britain, with 10,000 new cases each year. Worldwide, one per cent of those over the age of 65 are affected. Michael J Fox and Muhammad Ali are among those with the degenerative brain disease.

Last night, environmental campaigners warned that not enough is known about the dangers of the chemicals we use in our homes and gardens.

Elizabeth Salter Green, of WWF, said: "There are lots of man-made pesticides that attack the neurological system. Many of the fundamental building blocks of life, be it hormones or neurotransmitters, are exactly the same in all living organisms.

"So if you put a pesticide on the market that is good at killing a pest, you have got to be extremely circumspect as to what it is going to do to humans."

Previous studies have suggested that exposure to even small amounts of pesticides may play a role in Parkinson's disease and, last week, the Department for Environment, Food and Rural Affairs announced it was funding a £1million project to examine the link. In the latest study, the U.S. scientists examined data on over 140,000 men and women from a national survey.

Of these, exposure to pesticides was reported by 7,864 participants, while there were 413 cases of Parkinson's.

After taking into age, sex, and other factors such as diet and exercise, the researchers concluded that individuals who reported exposure to pesticides had a 70 per cent higher incidence of the disease than those who did not.

While farmers were more likely to have been exposed to pesticides, the development of Parkinson's was equally prevalent among other kinds of workers.

Potential sources of exposure include crop spraying, weedkillers, pesticides and insecticides used in the garden and fly sprays and ant powders used in the home.

Writing in the journal Annals of Neurology, the researchers said they did not find any link between the amount of time the men and women had been exposed to the chemicals and the risk of Parkinson's.

Nor was there any increased risk from exposure to other occupational hazards, including asbestos, coal or stone dust, chemicals, acids, or solvents.

Lead researcher Alberto Ascherio, whose work was part-funded by the Michael J Fox Foundation, said: "The findings of this large investigation support the hypothesis that exposure to pesticides is a risk factor for Parkinson's disease."

No specific chemicals or pesticides were named in the study and the researchers said more work was needed to examine which pesticides are likely to cause the condition.

Georgina Downs, of the UK Pesticides Campaign, said the finding was "highly significant."

Writing in the ME charity magazine Interaction, she said: "Pesticides, by their very nature, are designed to kill living organisms. People can be exposed to these chemicals via air, water, contaminated surfaces and food.

"Once pesticides have been absorbed, they can enter the blood stream and be carried throughout the body. Babies, children, pregnant women, the elderly and those with pre-existing medical conditions are particularly vulnerable to the effects."

She added: "Considering many pesticides are neurotoxic then it isn't surprising that study after study has found associations with various chronic neurological and neuro-degenerative diseases such as Parkinson's."

"This is highly significant in relation to the long-term exposure of rural residents and communities living near sprayed fields, where they can be repeatedly and frequently exposed to mixtures of pesticides, throughout every year and in many cases for decades."

Much fresh produce is also contaminated with pesticide residue.

Studies published last week by the Government's Pesticides Residues Committee found contamination in 39 per cent of food sold in the high street. A second, looking at free fruit given out in schools, found an even higher proportion — 66 per cent — contained one or more residues.

While most of the levels were below what is considered safe, two per cent of the samples from the high street study were above the legal limit. The Crop Protection Association said pesticides are vital to farming and gardeners and their use is strictly regulated.

Helen Lynn, of the Women's Environmental Network, said not enough was known about the safety of pesticides and other chemicals.

Kieran Breen, of the Parkinson's Disease Society, said: "This is the largest study of its kind and backs up other studies that have shown a link between exposure to pesticides and Parkinson's."

Last year, an official inquiry warned that families living near farms could be in danger from the spraying of pesticides and other chemicals.

The Royal Commission on Environmental Pollution said that spraying fields was a potential health risk and could be responsible for diseases including Parkinson's, cancer and ME.

The Government, however, rejected the commission's calls for buffer zones to be set up around farms, stating the pesticide-free zones would scare rather than protect the public.

Parkinson's disease is caused by the degeneration of nerve cells in the brain that send chemical messages to neurons controlling the muscles. Symptoms include tremors, stiffness and a gradual slowing down of the body.

As the disease progresses, speech, facial expression and balance can be affected and some sufferers end up in a wheelchair.