Sean Rickard of Cranfield University, Bedfordshire, a former chief economist for the National Farmers' Union and a member of government advisory bodies on agriculture, said loss of production would add £1 a kilo to the costs of potatoes and cabbages.

Reduced wheat yields would lead to 9p on a standard loaf, 3p on a litre of milk and 40p on a kilo of pork, and many farmers would be forced out of business.

Mr Rickard, who runs the Master of Business Administration programme for the Cranfield School of Management, near Bedford, was hired by agro-chemicals company Bayer, to report on the cost implications of the kind of yield losses already predicted.

Ministers from the Department for the Environment Food and Rural Affairs are appalled at the possible consequences, but the European Commission is trying to persuade everyone else that they will not be too bad.

The Yorkshire Post was among the first to report on the impact assessments written by the UK's biggest agricultural consultancy, Agricultural Development and Advisory Service (ADAS), which used to be part of Defra, and the government's own Pesticides Safety Directorate. (PSD).

The PSD named the substances which might be taken out of circulation in a report for Defra. Then ADAS estimated the effect on crops in a report commissioned by the pesticides manufacturers.

Mr Rickard's report is based on their work and EC officials in London say that means worst-case scenarios, based on "unrealistic" assumptions.

But James Clarke, who worked on the ADAS report, said the worst was still possible, because there was so much uncertainty over how the proposed new rules would work. Until the EC cleared up the confusion, all predictions were a matter of opinion to some extent.

Go to http://tinyurl.com/4g8eta for the full version of Mr Rickard's report.