As many as one in 20 pesticides sold in the European Union may be fake and could harm human health, according to the European Crop Protection Authority (EPCA). The illegal trade also costs £20 million a year in lost taxes, it said.

Criminals, mainly in India and China, are smuggling counterfeit insecticides, fungicides and herbicides into the EU to cash in on its agri-chemical market, which is worth £5 billion a year. It is thought that about 3 per cent of pesticides used in the UK are fake and that in the rest of Europe it could be as high as 7 per cent.

Two British firms are being investigated over the supply of bogus agri-chemicals by the Department for Environment, Food and Rural Affairs and enforcement agencies have been urged to monitor the problem more closely after the industry alerted the European Commission to the potential threat to human health.

The edition of Chemistry & Industry published today, the magazine of the Society of Chemical Industry, reports that the alarm was raised after a herbicide used on wheat in Italy was found to contain the potentially dangerous insecticide methidathion. It requires safe handling but was not mentioned on the label.

In Italy, Spain and France hundreds of hectares of maize, potatoes and tomatoes have been damaged by a fake herbicide and in 2002 a survey of produce in supermarkets in the UK found traces of eight potentially dangerous compounds.

The ECPA says illegal agri-chemicals now pose a greater risk than counterfeit medicines.

The Pesticides Safety Directorate has told farmers to avoid cheap deals and to buy chemicals from reputable sources. It has also has increased spot checks on sales of pesticides.

A spokeswoman for Defra said that the department was preparing to prosecute two firms but did not name them.

She insisted that the UK’s regulatory controls were robust and added that the Government had urged other EU members to increase surveillance to ensure that British citizens were not threatened by any unsafe food imports.

The problem has been exacerbated by companies attempting to sell products in the UK without a legal patent.

At a British Crop Protection conference in Glasgow last month, 24 companies — 23 Chinese and 1 Indian — were given legal warnings and three were ordered to cease commercial activity, after illegally promoting products.

A spokesman for the Food Standards Agency said: “It [the sale of bogus agri-chemicals] is unlikely to pose a risk to public health because there is a rigorous pesticide residue monitoring programme in place.”

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