Up to three quarters of the poultry labelled as halal is not in fact halal, leading producers have warned.

Approximately three-quarters of poultry and a small volume of beef and lamb sold as halal in the UK are slaughtered by machine rather than an individual, Eblex Halal Steering Group member Naved Syed claimed. As the slaughter method was not usually printed on labels, the meat was essentially being passed off as halal, he said.

"If you told Muslims it was done by a machine they wouldn't buy it," he said. "Practically all imams in this country have said that machine killing is not halal. Otherwise there's no difference between halal and non-halal."

Many Muslim countries have outlawed the practice after the internationally recognised Malaysian Halal Standard MS 1500 removed machine slaughtering as an acceptable practice last year. The standard is not widely adopted in the UK, where several certification bodies operate.

The Birmingham Council of Mosques last week said it did not accept machine slaughter. The body would call on the FSA to get machine-slaughtered meat off the halal plate, said representative Ruksana Shain.

Britain's two million Muslims consume 40% of all the poultry and 27% of the beef and lamb sold in this country, according to Syed. Eblex is carrying out consumer research to establish attitudes to halal production so the Halal Steering Group can devise the best way forward.

"Machine slaughter is definitely not a lawful condition of halal you have to have a manual slaughter and also each bird needs to be blessed," said Zahid Hussain, chairman of Cappoquin Poultry.

Another poultry supplier argued there was no consensus on acceptable halal methods. "There is a lot of politics between different bodies and in the standards themselves," he said, comparing the split among Muslims over slaughter methods to divisions in the meat industry when farm assurance standards were being developed.