Conventionally produced food has come out on top in a poll on organics on Waitrose's website.

More than two-thirds of visitors to the site said they preferred conventional agriculture, compared to 32.2% in favour of organic farming.

Against the backdrop of organic food fortnight, the supermarket also organised a head-to-head debate between Soil Association director Patrick Holden and the NFU's director of communications Anthony Gibson. While it was predictably lively and included accusations of mumbo-jumboism from Gibson, the pair finally found common ground over the issue of locally sourced food.

Holden urged Waitrose to take more of a lead on food miles and warned that all retailers would have to follow suit.

"Food security is going to be a huge issue in the future, largely due to rising energy costs," he said. "The move towards localism will pose a challenge to all supermarkets, because their distribution is centralised at present."

He also predicted that British farming would be forced to make wholesale changes to a less intensive and more environmentally friendly form of production in the next 20 years.

"With global warming and other environmental threats, it is in the public interest for there to be a

radical shift in farming

practices," he said.

Gibson agreed and said he hoped Holden was proven right. "I wish the organic movement every success. If it continues to grow, conventional farmers will continue to convert in order to supply it."

But he warned that the premium for organic food might not survive a global rise in food prices.

"It is possible that the world will run short of food in 30 or 40 years from now because of biofuels, climate change and the rising population," he said. "If food is more expensive, I'm not sure people will still be prepared to pay a significant premium for organically-produced food."