The vision of hi-tech British farming outlined this week by the UK government's chief scientific adviser, Sir John Beddington, has been dismissed as unnecessary and potentially damaging by environmental groups and organic farmers.

In a speech to British farmers and the food industry on Wednesday, Beddington claimed there was a need for "a new and greener revolution" to increase food production. He urged that genetic modification (GM) of crops and nanotechnology needed to be mobilised if catastrophic food shortages were to be avoided in the face of rising temperatures and global population.

"Techniques and technologies from many disciplines, ranging from biotechnology and engineering to newer fields such as nanotechnology will be needed," he told the Oxford farming conference.

But the hi-tech strategy, known to be favoured by the environment secretary, Hilary Benn, and the government, came under attack by organisers of the Oxford Real Farming Conference, meeting in the city at the same time. Here, academics, environment groups and others concluded that farmers were well able to feed the world without novel and untried technologies - but to do so would require governments to operate in line with biological principles and not solely economic ones.

"For decades politicians have starved agriculture of resources on the mistaken notion that the market would deliver a secure food supply," said biologist and writer Colin Tudge. "As a result tens of thousands of farmers have gone to the wall and Britain has been robbed of the skills it needs to feed the people."

"The government has recognised that we're now in trouble and are desperately pinning their hopes on untried GM technology to save us. But scientists who truly understand agriculture know that this can't solve our food supply problems. The real answer is to redesign agriculture from first principles. But this time our prime objective must be feeding people, not making profits for large business corporations as now," said Tudge.

Emma Hockridge, policy manager of the Soil Association, said Prof Beddington's approach was not the best way forward. "GM is not going to feed a growing world population sustainably, now or in the future. We need far-reaching changes to our food and farming systems, rather than GM technology, which, despite millions in public and private research expenditure, has consistently failed to deliver food security."

Martin Wolfe, the research director of Organic Research Centre, Elm Farm, said there were still many unanswered questions about GM crops and the monoculture systems they were designed for. The only realistic way to maximise productivity was through "polycultures" in which a wide variety of crops and animals are integrated. "The first priority for research and development should be for ecological agriculture," he said.

"The dangerous obsession with GM crops must end," said Helen Rimmer, of Friends of the Earth. "The most comprehensive farming report ever conducted found no conclusive evidence that GM increases yields and called for a move away from damaging industrial farming. The majority of GM crops are grown for animal feed, many on massive plantations that have replaced South American rainforests. GM crops don't feed the world - they simply make record profits for the big businesses that sell the patented seeds and chemicals needed to grow them."

The chief scientific adviser for the Department for Environment, Food and Rural Affairs, Bob Watson, has called for UK trials of GM foods, arguing that the government needs to be more open with the public about the risks and benefits of genetically modified foods.

"Over the next 20 to 50 years, the population is going to increase from 6.5 to 9 billion. There will be more extreme weather, more demand for food, meat, and water, a changing climate," said Watson in November. "We have to look at all the technologies, policies and practices, all forms of bio-tech, including GM."

Critics of GM point out that a UN-sponsored four-year review, involving more than 400 international scientists and chaired by Watson, concluded in 2007 that GM technologies were unlikely to have more than a limited role in tackling global hunger.

According to the Watson-led review, the scientific evidence on the claimed benefits of GM suggests they are variable, with increases in yield in some areas but decreases in others, and both greater and lesser pesticide use in different contexts. The report concluded that global hunger is as much to do with power and control of the food system as with growing enough food.