Makers of bottled baby food have been urged to change the packaging after a toxin linked to cancers and birth defects was found in several varieties contained in glass jars with metal lids.

The discovery of semicarbazide three months ago in dozens of foods packed in jars and bottles with twist-on-twist-off lids sent the food industry into turmoil, prompting an investigation by a panel of scientific experts reporting to the European Food Safety Authority.

The substance, also called SEM, has been linked in animal studies to cancers, liver damage and - in high doses - to miscarriages and birth defects.

So far it has been found in bottles or jars of baby food, fruit juices, jams and preserves, pickles, mustard, honey and sauces such as ketchup and mayonnaise.

Yesterday Dr Sue Barlow, the panel's chairman, told the food industry "It would be prudent to reduce the presence of semicarbazide in baby foods as swiftly as technological progress allows." The authority also recommended a reduction of the chemical in other foods, after baby foods have been tackled.

Contamination of food products with SEM was first discovered by an independent laboratory used by Nestle, Heinz and other food makers, although none of the companies would admit that its foods were among those contaminated.

Scientists believe SEM is produced during the heat treatment used to make plastic sealing gaskets in the lids of glass jars and bottles. The chemical then migrates from the plastic into the food, Dr Barlow said.

The Food Standards Agency in London said yesterday that it had commissioned its own research to develop a reliable test for semicarbazide. It has also been consulting the Metal Packaging Manufacturers' Association.

Sir John Krebs, chairman of the agency, said that there was "considerable uncertainty about the possible risks from semicarbazide". He said it was not possible to rule out that the chemical was a cancer risk to humans. But he said that, according to the expert panel, the risk was "very small".

Sir John did not advise against eating food from jars but said that "parents may understandably be concerned by the continuing uncertainty, which may lead some to choose alternative foods for their babies".

The agency said parents who wanted to avoid glass jars and bottles of baby foods should look at frozen, tinned and packets of dried baby food. It has published practical suggestions on its website on how parents might make their own baby food.

Martin Paterson, the deputy director general of the Food and Drink Federation, which represents manufacturers, said a joint food and packaging industry task force was "working with the authorities to eliminate SEM from the metal twist caps used with glass jars".

He said it would take some time to find a replacement for the current sealing technology.

A spokesman for Nestle said the company had alerted authorities as soon as it was aware of the problem. Monique Warnock, a food campaigner at the Consumers' Association, said there were concerns that although the potential health risk was sufficient for the European Food Safety Authority to urge manufacturers to change their packaging, it did not warrant the removal of these containers from shops.

"The food industry identified this potential risk. It needs to show its commitment to consumer safety by taking immediate action to find alternative sources of packaging," she said.