Geoffrey Forse, a spokesman for the city's Green Party, says that the council should not serve genetically modified food to children until it is seen to be completely safe.

The Green Party says the long-term impact on children's health cannot yet be known

In response to questions from the Green Party, the city's education committee has agreed to investigate the use of modified food in school dinners, promising to report back to councillors in January.

Describing genetically modified produce as "Frankenstein food", the Green Party wants a longer period of study before foodstuffs including types of soya and tomato are included in school dinners.

"We should learn the lesson of BSE," says Mr Forse. "The dangers took a long time to work through and we shouldn't take any risks until we know the food is absolutely safe."

Soya products are among the genetically modified foods in school dinners

"The idea of taking a gene from a fish and putting it into a tomato isn't natural - we just don't know the long-term consequences for health.

"If there is any question about its safety we shouldn't serve it to children. We should take things slowly - there might not be a cause for concern, but we can't be certain," said Mr Forse.

A spokeswoman for Leicester City Council said that at present only a small amount of genetically modified food was used in school dinners.

The council, which still excludes beef from its school dinners, will make an investigation into the available evidence before presenting its report in January.