Prince Charles has warned that the adoption of genetic modification in farming has set the world on course for "the biggest disaster, environmentally, of all time".

In an outspoken assault on GM crops, the prince accused unnamed "gigantic corporations" of "conducting a gigantic experiment with nature, and the whole of humanity, which has gone seriously wrong".

In an interview given to the Telegraph at the Castle of Mey, a Windsor family seat in Caithness, the heir to the throne reiterated his antipathy to industrialised agriculture.

He delivered a vividly-worded prediction that small farmers across the globe would be forced from their land into city slums through companies planting GM crops.

"We [will] end up with millions of small farmers all over the world being driven off their land into unsustainable, unmanageable, degraded and dysfunctional conurbations of unmentionable awfulness," the prince said.

"What we should be talking about is food security, not food production - that is what matters, and that is what people will not understand.

"And if they think it's somehow going to work because they are going to have one form of clever genetic engineering after another, then count me out because that will be guaranteed to cause the biggest disaster environmentally of all time."

As evidence, the prince cited environmental problems in countries which have used GM crops to increase food production.

He said he had seen first hand the result of over-demand on irrigation systems and the water table in Punjab because of the hybrid seeds and grains used.

"Look at Western Australia," he added. "Huge salinisation problems. I have been there, seen it ... some of the excessive approaches to modern argriculture."

Prince Charles first set out his opposition to GM crops in 1998 when he said that "genetic modification takes mankind into realms that belong to God, and to God alone".

His latest remarks are likely to set him against the British government, which has approved 54 trials of GM crops since 2000, the latest being a trial by the chemical giant BASF to test a blight-resistant potato at a site in East Yorkshire.

However, Europe is proving more resistant to the spread of GM crops than the rest of the world, and no GM crops are being grown commercially in the UK.

Almost all the trials to have taken place in Britain have been disrupted by protesters.

Meanwhile, the area planted with GM crops worldwide has soared almost 70-fold in 10 years to 114m hectares.

That is predicted to double by 2015, according to a report published in February by the International Service for the Acquisition of Agri-biotech Applications, a GM industry group.

Greenpeace believes the spread of GM crops has been "a disaster" and that they "pose a serious threat to biodiversity and our own health".