GENETICALLY modified crops are everywhere, it seems - even in Europe. Strict laws designed to keep the European Union free of unauthorised GM crops and products are not working, and are posing problems for the EU's €150 billion livestock industry, according to farmers' representatives. They say that supplies of animal feed for poultry and pigs are being refused entry at European ports when found to contain even trace amounts of unauthorised GM material.

Under Europe's "zero-tolerance" laws on GM contamination, introduced in 2007, the presence of even a few seeds of unauthorised GM material will rule out an entire shipment. The animal feed industry says that the laws are unworkable because GM material is almost ubiquitous, given today's global supply chain.

"Though we understand the consumer concern in Europe, we don't understand zero tolerance because it closes down trade," says Pekka Pesonen, secretary general of Copa-Cogeca, a coalition of groups representing 15 million EU farmers in total. He claims that European pig and poultry farmers will go out of business unless the EU adopts a more pragmatic screening approach by setting a threshold - say 0.5 per cent - beneath which GM contamination is tolerated.

Pesonen says such "tolerances" operate for other contaminants, including pesticides and heavy metals. So why not for GM material, much of which has been cleared for human consumption elsewhere in the world?

Last year 200,000 tonnes of conventional animal feed - mainly soy and maize - were refused entry to the EU when they were found to contain small amounts of GM maize varieties. Then flax from Canada was found to contain traces of a GM variety named CDC Triffid that was withdrawn from commercial sale in 2001. Following a ban on flax more than 100 shipments were rejected, but trade is slowly resuming.

The rejected tonnage is only a fraction of the 32 million tonnes of feed imported each year. But it leads to delays to subsequent consignments, higher prices and a reluctance by importers to risk further shipments.

Prices will be higher still this year, says Pesonen owing to droughts in South America and a growing market for American farmers selling crops to China, which accepts mixed shipments.

Increasing numbers of GM crop varieties are on the way. At present, around 30 varieties are grown around the world, but that is predicted to quadruple by 2015, making screening trickier than ever.

A further complication arises because all the European commissioners are due to be replaced in February. A spokeswoman for the health commission, which introduced the zero-tolerance policy to satisfy widespread misgivings in Europe about the safety of GM crops, says that "intensive consultations" on feed imports have already taken place. "Once the new commission is established, it will have to consider how to proceed on this matter," she says.