Trials of GM crops are due to finish later this year

Michael Meacher - sacked as a minister in the recent reshuffle - said studies on the effects of GM foods on human health had been "scientifically vacuous", and warned the government against rushing the debate.

Agency chief executive John Bell said Mr Meacher was entitled to his opinion but the FSA relied on the advice of experts.

Mr Bell told BBC Radio 4's Today programme: "What the trial showed was DNA was fully broken down in the gut but in the early part of the gut it's only partially broken down and that's the same for conventional foods as for any other type including GM.

"We don't consider it is potentially worrying."

The researchers had looked "very carefully" to see the extent to which the DNA was being broken down.

"Some fragments seem to have been taken up by the gut bacteria but I have to emphasise that these were only fragments - they were not functional genes and they served no purpose.

"There's no reason to believe that ordinary fragments of DNA in any other food wouldn't be taken up in a similar way."

No proof of risk?

On Monday, Mr Meacher's successor, Elliot Morley, said GM foods had never been shown to pose any risk to human health

"There have been studies in this country, there have been studies in France, there's been studies by the food and agricultural organisations of the UN," he said.

"There have been lots of studies in terms of toxicology, in terms of potential allergies, in terms of potent health risks, in any of the existing products there has never been any indication there has been a health risk."

Writing in the Independent on Sunday, Mr Meacher said the only human GM trial commissioned by the Food Standards Agency found genetically modified DNA did transfer to bacteria in the human gut.

Many scientists had denied this was possible.

Mr Meacher is unconvinced by GM crop tests

"But instead of this finding being regarded as a serious discovery which should be checked and rechecked, the spin was this was nothing new and did not involve any health risk," he said.

Mr Meacher - a veteran of the Wilson and Callaghan administrations - was widely believed to be at odds with the prime minister over his stance on GM foods.

In his article, Mr Meacher accused the government of deliberately undervaluing negative research findings on the safety of GM foods.

He said scientific reports indicating possibly damaging effects on humans had been "widely rubbished in government circles".

'Very worrying'

And the debate on GM foods had been deliberately stifled with pressure from bio-technology companies, he said.

He said a public debate on the GM issue was under way, and people were welcome to contribute views.

Liberal Democrat environment spokesman Andrew George said Mr Meacher's comments "blow a hole in any claims the government might make about their desire for an open debate on GM".

Anti-GM campaigners welcomed Mr Meacher's comments.

GM crops have attracted widespread opposition

Pete Riley, of Friends of the Earth, said they confirmed the fears of those who suspected the government-funded debate on the GM issue was a mere PR exercise aimed at getting the green light for GM crops to be grown in the UK.

Patrick Holden, the director of the Soil Association, which campaigns for organic food and farming, said: "Mr Meacher's comments are very worrying because they suggest the government has already made up its mind on GM."

The government launched a series of nationwide public consultations on GM crops earlier this month.