The prime minister has insisted that future decisions on GM crops will be based on "science and not prejudice".

Warning that Britain could be left behind if it allows dissenting voices to win the argument without good reason, he said further scientific research would be necessary.

"We will act according to the scientific evidence," Tony Blair told the Commons.

"I think the system that we have set up is one that is robust because it is allowing us to get proper scientific evidence."

He conceded that there were "problems of biodiversity" for some GM crops but signalled that future decisions would be based on sound science and not lobbying by interest groups.

"I know there is a huge campaign against GM and to be frank about it the government has got no interest in this one way or another other than to do the right thing," he said.

And he warned that Britain would make a huge error if it simply rejected the GM issue.

"The biotechnology industry is a vital part of this country's industry," said Blair.

"There are many people who believe that the whole science of genetics is going to be the science of the first half of the 20th century.

"There are other countries piling investment into this area and therefore I think we have simply got to proceed with care."