Consumers are being routinely exposed to unsafe levels of pesticide residues in their food which are nevertheless still within legal limits, campaigners warn today.

More than 5% of fruit, vegetables and other foods carried harmful pesticide residues which posed "appreciable" health risks to consumers. One pesticide, Imazalil, exceeded the safe limit on 79% of oranges sampled, according to the Pesticide Action Network.

Imazalil is "moderately hazardous" and a likely human carcinogen, according to the World Health Organisation, but most of the pesticide might be in the peel and therefore not eaten.

Apart from oranges, about 1.6% of fresh produce was found to contain pesticides above internationally agreed safety levels, which means that anyone eating large quantities of fruit and vegetables might expect to exceed the safe intake five or six times a year.

The Pesticide Action Network conducted its own analysis of official government data. The government's own pesticide residues committee report for 2005, due out in the next few days, will analyse the same data.

The campaigners' report indicates that more rigorous safety checks are needed to allay consumers' concerns about pesticide residues in their food. They can lead to chronic illnesses and cause disruption to endocrine systems at low doses.

The campaigners analysed the data to show which foods are most likely to be contaminated with pesticides and which pesticides appear most frequently. They also give advice - such as eating organic - on how to cut pesticide intake while still eating the recommended five or more portions of fruit and vegetables a day.

The government report generally focuses on the legal limits of pesticides in food, which are set by the EU. Yet this limit, known as the maximum residue level, does not actually relate to how safe the pesticide is.

The campaigners' analysis of the government's 2005 data compared residues against the safety limit for consuming an amount that would be eaten within one meal, or a day. This safety limit was exceeded in 97 cases, indicating that there could be an appreciable health risk to the consumer. These samples were at levels typically between 100% and 500% of the safety limit, although one sample reached 1,600%.

Clare Butler Ellis, of the Pesticide Action Network, said: "The pesticide residues committee almost always find no cause for concern with these levels of pesticides, but we think the public are right to be concerned and to try to do something about it."