Euro-MPs today backed tough new rules restricting the use of pesticides in crops - despite warnings that food prices would rise and production fall.
The UK Government, which opposes the move, will now vote against the plan when it comes up for approval by EU governments.
Changes in the way pesticides are assessed and authorised for use on crops are part of an EU goal to halve the use of toxic products in farming by 2013.
But the scale of the plans has been attacked by the National Farmers' Union and the Crop Protection Association as too tough - threatening the UK's total carrot yield and 20 per cent of cereal production, as well as hitting everything from potatoes and onions to parsnips.
Conservative MEP Robert Sturdy said: "This law will drive up the cost of the weekly food shop at the worst time for British families.
"We do need strong restrictions on pesticide use but it should be based on sound science, rather than on the whim of politicians. There has been no balance whatsoever in the parliament's position. MEPs have failed to see pesticides as necessary tools in maintaining our crops.
"Many of the products on the market today are safe when used correctly, and have been around for years. Without crop protection products, our food supplies will be volatile at a time when food security is rising up the political agenda. "
Tory and Labour MEPs opposed the move, calling for a full impact assessment before any changes were approved.
Mr Sturdy added: "It is ludicrous that such a plan would be brought into law without an impact assessment to gauge its consequences. The only hope we have is for a last-ditch effort by the Government to demand we finally get an overall picture of how food production will be affected across the EU."
The proposed changes, altering the way pesticides are assessed for safety, and ultimately removing at least 22 toxic substances from use, were overwhelmingly backed by 577 MEPs, easily exceeding the necessary 393 threshold required to approve the measures.
But ministers still have the last say, and before today's vote Environment Secretary Hilary Benn said: "These regulations could hit agricultural production in the UK for no recognisable benefit to human health, and we are being asked to agree to something here when nobody knows what the impact will be.
"While we have managed to secure some improvements surrounding the use of certain pesticides, the UK does not support these proposals."
Some farmers have predicted a 50 per cent loss in potato yields and the loss of the entire carrot yield.
Tory MEP Daniel Hannan commented: "Where is the evidence that any of the proscribed pesticides are deleterious to human health? We don't know that the designated substances are harmful, runs the reasoning; then again, we don't know that they aren't."
Mr Hannan said legislators were using the "precautionary principle" - basing the pesticide safety test on "perceived hazard" rather than the current method of using a scale of scientific-based risk.
The change means ruling out pesticides which, if used correctly. are now considered safe despite containing potentially-dangerous products.
Mr Hannan said: "The precautionary principle puts farmers in the impossible position of having to prove a negative. Two hundred years ago, it was widely assumed that the noise of a passing train would cause pregnant women to miscarry. Had we applied the precautionary principle, we would never have laid an inch of track, since the rail operators of that day could no more prove that they wouldn't cause miscarriages than the chemists of today can prove that their products won't poison us.
"Apply a little common sense, for heaven's sake - no pharmaceutical company wants to sell a toxic product, and thus open itself to colossal liabilities."