Specialists on the UK Government's Advisory Committee on Novel Foods and Processes (ACNFP) are concerned about plants being grown in the USA and parts of Europe that contan a gene resistant to antibiotics.

They fear the resistance could be spread widely throughout the environment, and that it could be picked up by bacteria that cause serious disease.

Microbiologist Dr John Heritage, a member of the committee, has written to the American authorities to express his concern.

Gene transfer

Dr John Heritage: "This could make disease more difficult to treat"

Dr Heritage told the BBC the risk posed by antibiotic-resistant foods was small.

But he said: "We are talking about diseases that may be life threatening, like meningitis.

"Were these genes to get into bacteria from genetically modified plants it would make cases of disease more difficult to treat."

Dr Heritage said antibiotic resistant genes were used by biotechnology companies because they allow scientists to move other genes around.

Scientists do this with the aim of eradicating weaknesses in the crop and enhancing the positive qualities of the food.

Cells split

He said the risk of spreading antibiotic resistance occured when cells were broken open during the processing of the food, releasing the modified DNA into the environment.

The risk was magnified when the processing created dust, Dr Heritage said, because the dust would be breathed in.

"This is where the meningitis worry comes because a significant minority of the population carry the bacteria that cause meningitis," he said.

"That family of bacteria are very adept at taking up DNA from the environment and expressing it."

There are concerns about an antibiotic resistant gene known as AAD that is found in genetically modified maize and cotton.