BBC Chief Political Correspondent John Sopel: "The government have been on the losing end"

Dr Arpad Putsztai said that since October the Scottish Office had refused to release an "alternative report" on the research, according to the Scotsman newspaper.

It obtained a letter said to be written by Dr Putsztai to a sympathiser, in which the scientist accused Scottish Health Minister Sam Galbraith of "sitting on our conclusions".

It reads: "At least some MPs ought to know that there has been a cover-up, so that when the whole truth is revealed, they cannot say, 'I am afraid I did not know what was going on'.

"Let us hope that eventually everything will be revealed as in a civilised democratic society it should be."

The Scottish Office said it had received the alternative report as a matter of course, but it was up to Dr Puztai's former employer, the Rowett Research Institute (RRI) to publish it.

Dr Putsztai: His research suggests GM foods are harmful

Dr Putsztai was suspended last year from his post at the RRI in Aberdeen after saying his research showed that rats fed with GM potatoes had suffered immune system damage.

He is barred from speaking publicly about the affair.

Research released on Friday gave fresh support to Dr Putsztai's previously discredited findings.

The row deepened on Sunday following newspaper allegations that the Rowett Institute received £140,000 from Monsanto, one of the leading companies in the GM industry.

The government refuses calls for a moratorium on GM food research.

But public concerns remain. A weekend poll on the BBC's teletext service Ceefax received 10,392 calls from viewers saying they would not eat genetically modified potatoes - 280 people rang to say they would.

Government 'underplaying' GM use

The government has also come under attack from the campaigning group GeneWatch for allowing "the GM situation to get out of control".

GeneWatch said that more GM products were being used in food production than the government has admitted to.

According to the government, the only GM food products now on sale are tomato paste, some soya and maize, and cheeses made with a GM rennet.

But GeneWatch said 12 other GM enzymes were licensed for use in a wide range of processed foods.

"No-one knows the true extent of GM in food because so little of it is labelled or monitored," said GeneWatch director Dr Sue Mayer. "It could be used in up to 90% of processed foods in our supermarkets."

Supermarket labels praised

But the Consumer Association praised supermarket labelling, saying a voluntary code of practice exceeded European law on GM food. Current rules introduced last September require certain specified GM soya and maize products to be labelled as such.

The consumer watchdog's spokeswoman said: "We believe that all products that are derived by the process of genetic modification should be labelled.

"The EU regulation that is currently in place doesn't even go as far as some of the supermarkets have. They have taken public opinion and concern about GM products on board."