In his most passionate defence so far of GM foods, he told the Daily Telegraph newspaper the biotechnology industry could be as important to the next century as the computer had been to the current one.

But "scaremongering" without proper scientific evidence could mean the UK losing its lead, he said.

The government's refusal to impose a moratorium on the development of GM foods has been under attack after scientists warned of serious potential health risks.

Mr Blair has said GM food is welcome at Downing Street

Environmental groups want to freeze development for five years while more tests are carried out.

Mr Blair vowed to resist the "orchestrated barrage" from the media and the "tyranny of pressure groups".

If successful GM technology could lead to the development of cheaper, better foods, while reducing farmers' reliance on harmful pesticides and herbicides, he said.

He stressed that the government was committed to consumer safety.

"There is no scientific evidence on which to justify a ban on GM foods and crops.

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Political correspondent Emma Udwin reports on Mr Blair's "personal crusade"

"If we were to ban products that our independent scientific advisers tell us are safe, we would send a negative message to the whole biotech industry in the UK - in healthcare as well as in food and in agriculture - that its future will be governed not by evidence but by media scares," he said. 'Maximum benefits'

But Mr Blair's message was questioned by environmental campaigners, who warned that serious questions remained over GM food.

Friends of the Earth policy and campaigns director Tony Juniper said: "If Mr Blair really is concerned that society gains maximum benefits from biotechnology he should do three things.

"The first is to announce a five-year moratorium on the import of genetically- modified food and the commercial growing of GM crops in this country.

"The second is to show that the government is not under undue pressure from the United States and biotechnology companies in rushing forward with this technology.

"The third is to eliminate any conflicts of interest between ministers' official duties and industrial development of biotechnology."

Greenpeace director Dr Doug Parr said in a statement: "The stampede Blair is experiencing is not coming from the media and pressure groups but from the public at large who want these gene crops and food banned.

"Blair's vision is simply swallowing the agro-chemical industry's hype and its justifications which, like its often touted 'feed the world' argument, don't stand up to scrutiny.

Website warning

Mr Blair's defiant message came the day after the government launched a public information campaign on GM food using the Number 10 Downing Street Website.

The Internet campaign hits back at newspaper reports on GM foods. It insists no split exists on the testing of GM crops between the government and its adviser English Nature.

And it rejects allegations that the British people are being used as guinea pigs for untested new foods.

The government has also released a letter by five leading ministers to MPs to put the case against a ban on GM crops and reassure them public safety was the top priority.

The letter was signed by five key ministers - Deputy Prime Minister John Prescott, Health Secretary Frank Dobson, Cabinet Office Minister Jack Cunningham, Agriculture Minister Nick Brown, and Trade Secretary Stephen Byers - and accompanied by a 50-page factfile.