"Dr Williams is living in 'cloud cuckoo land' if he thinks we can make the UK self-sufficient in food production and still allow consumers to enjoy the wide variety of fruit and vegetables they want," said the Fresh Produce Consortium (FPC).
"His call to mobilise Britain's gardeners and transform our gardens and parks into vegetable plots to feed the nation is ridiculous."
The FPC said around 60 per cent of fruit and vegetables were imported, providing us with produce outside the UK season as well as varieties that could not be grown at home.
Williams made his comments to the press on the eve of a climate change lecture he gave on Tuesday 13 October. He suggested Britons should eat less food air-freighted from places like Kenya and get in touch with "the natural rhythms of the seasons".
The FPC countered that research showed some imported fruit and vegetables were grown in less greenhouse-gas-intensive ways than the same products in the UK. It said: "There's no need to restrict choice by excluding imported produce on the basis of its carbon footprint.
"We can enjoy a wide variety of fresh produce all year round, irrespective of its origin. The consumption of fruit and vegetables accounts for only 2.5 per cent of the UK's greenhouse-gas emissions in total."
There was no evidence that fewer aircraft would fly if less imported fresh produce was eaten, added the FPC.
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