Western Daily Press (Bristol)

In fact, it is now estimated that up to 60 per cent of products on supermarket shelves contain some genetically modified (GM) ingredients.

As public disquiet grows about these so-called 'Frankenstein foods', a group of more than 100 leading food writers have waded into the debate and are backing a Greenpeace campaign for a ban on GM food.

But how much does the consumer know about GM food, and should we boycott it to try to prevent a food crisis that has the ability to make the BSE saga appear puny by comparison?

Since plants were first cultivated, many have been selected for improved yield, growth, colour and taste. Genetic modification focuses on the root of these improvements: The genetic code.

The plant's characteristics are defined by its DNA code. Nowadays, genetic engineers can take genes from one species and insert copies into another without the need for the plants to be sexually compatible.

Since 1983 all major crops have been modified, including maize, oil-seed rape, tomatoes and potatoes.

And it's no bad thing, according to Alex Woolfall, spokesman for the American food giant Monsanto, which is at the cutting edge of the revolution in genetically-modified crops.

He says: ''The idea seems to be that the public are being used as guinea pigs in some huge genetic experiment but nothing could be further from the truth.

''No GM food gets manufactured until it has been approved by seven different scientific committees and four different Government departments.

''What's worrying is that these campaigners are scaremongering without basing it on fact.''

Woolfall claims that GM crops require less herbicides because of their in -built protection. He also envisages a future in which a more solid potato will be developed which could be used in the production of chips and crisps with reduced fat.

And developing countries could also benefit with an enhanced oil seed rape which could increase the amount of beta carotene, and so wiping out a Vitamin A deficiency that could lead to blindness.

The health and nutritional benefits sound impressive and the technology appears to offer huge potential for feeding the world's projected population of eight billion in 2020.

But food writer Lynda Brown, author of The Shopper's Guide To Organic Food, says she has chosen to back Greenpeace's campaign for a ban on GM food because she is in exactly the same position as the consumer: Ignorant.

As a self-confessed defender of food quality, she is furious that GM foods are being 'imposed' on the public.

And she scoffs at the idea that the foods have been tested satisfactorily, pointing out that multi-national companies backed the pesticide DDT, which turned out to have toxic properties.

She says: ''Another frightening scenario is that Monsanto are buying up seed companies, giving them complete control of the food chain.''

Brown also says the problem could be a time-bomb - and the effects will not be discovered for decades.

The problem for consumers, she believes, is that labelling regulations are so unclear they are virtually useless. Indeed, she is positive that, without knowing it, she has eaten GM food.

She says: ''I'm sure I probably have. Sixty per cent of all processed food contains GM soya. The consumer wants the choice to be able to buy GM-free food but we are not given that choice.''

But she believes the fight can be won. "We are literally on the cusp here. The supermarkets and food industry are looking at GM food and asking which way they should go. We might be David against the Goliath of the food companies but this one is winnable.''

Should Britain wholeheartedly embrace GM food, many experts fear the consequences of eating genes that are totally foreign to our bodies.

Malcolm Walker, chairman of Iceland foodstores, was backed by Prince Charles when he banned GM ingredients from the company's 2,000 own-label products last May. The food industry and rivals ridiculed him as 'Canute- like'.

But Walker is adamant that he has followed the right path. He says that GM soya is in chocolate, biscuits, beer, pies, flour and vegetarian products, either as raw protein or as a soya derivative.

He said: ''You can't avoid it. What got me was they had obviously decided that the only way the public was going to accept it was if it was mixed with non-GM soya. It started being just two per cent that was modified mixed with 98 per cent non-modified. Now that figure has increased to more than 50 per cent.''

Walker admits when he first tackled suppliers they told him it was not possible to ban GM products.

''There was a lot of pressure on us to back down. Suppliers would say they didn't want the public frightened by another BSE type scare. I explained that was exactly the reason why I was doing this. We certainly weren't popular.

''We also got a lot of people saying they would never have expected Iceland to do it. Maybe they expected it to be Waitrose. Just because we sell fast food doesn't mean it shouldn't be good food.''

Eliminating GM food has not been easy, as it comes in all shapes and forms. For example, the pepper used in the seasoning of fish fingers contains a lecithin - a GM soya derivative.

But Walker is adamant that the message is starting to get through as other manufacturers begin to swap to GM-free food.

He says: ''Our technological manager is in great demand to speak all over the world. Other manufacturers want to know how we did it.''