The Prime Minister's approach, in an interview on BBC Television's Breakfast with Frost programme, was in marked contrast to his attack last month on the "media hysteria" about GM foods. His rethink follows the Prince of Wales's broadside over the Government's handling of the issue.
Several Labour MPs have warned party whips that they are receiving a stream of complaints from the public about the Government's strong support for the industry. "It's the number one issue," one backbencher said yesterday. "People are very worried about this."
Mr Blair insisted that banning GM foods would risk throwing away Britain's lead over other countries in biotechnology, at a time when Germany was spending hundreds of millions of pounds on catching up.
"Britain is at the leading edge of this new technology, particularly in relation to medicines. It could indeed be the leading science of the 21st century," he said.
Denying suggestions that the Government was a "great advocate" of GM food, he said: "I'm not the advocate of anything other than keeping an open mind."
Mr Blair said it would be a mistake to ban the new technology, a move which might be proved wrong in 15 or 20 years time. "At the moment I think the jury's out, which is why we've got to have these trials and have scientific evidence done very, very carefully indeed," he said.
He appeared to acknowledge the Government was out of step with public opinion, saying no politician wanted to be in that position. "I know it's a very unpopular thing to say, but sometimes it's important to say to people look, there is another argument," he said.
"We have to proceed according to basic evidence and not simply say because people talk about Frankenstein foods, we chuck the whole thing out of the window."
When challenged by Sir David Frost, Mr Blair did not deny a report in The Independent on Sunday yesterday that his wife Cherie privately shares Prince Charles's concerns about the safety of GM foods.
Michael Meacher, the Environment Minister, who has adopted a more sceptical stance than Mr Blair over GM produce, said yesterday that Prince Charles had "an important contribution to make" and that the Government was anxious to talk to him. Mr Meacher admitted there were "very great uncertainties" about the new technology. "I'd be the first to recognise that the existing level of research does need to be supplemented," he told GMTV. "We need to continue monitoring and regulating in the most stringent way to be absolutely sure."
He insisted that biotechnology should not be rejected, but said the public was quite right to be concerned about it. "It would be quite wrong to dismiss all the concerns.... There is a genuine and perfectly proper concern ... about this."