Kosher meat producers have reacted furiously to a study which claimed their prices had soared in the past decade.

Butchers said the figures had been "manipulated" to ignore market forces and increased production costs.

The report by economists Anthony Tricot and Andrea Silberman - published in last week's JC - calculated that kosher meat prices had doubled, while non-kosher prices had risen by 40 per cent.

Jacky Lipowicz, Licensed Kosher Meat Traders' Association chairman, said members had regularly slashed prices because they knew Jewish customers were struggling to afford staples such as chicken.

He said rising global feed prices meant the small kosher industry would continue to face challenges.

The quality and safeguards associated with kosher meat also warranted further consideration, Mr Lipowicz argued. He said: "What did Tesco have in their supermarkets? Horse. Because no one checked it. That supervision costs money. You get what you pay for."

Stephen Grossman, owner of the Silvermans chain of butchers and Lewco Pak poultry production company, said: "The comparison was not a true reflection of a specific dietary requirement against a mainstream process."

London-based Mr Lipowicz challenged Mr Tricot and Ms Silberman to repeat their figures in a public debate. "I will shoot them down in flames," he said. "They have got a hidden agenda."

London Board for Shechita chief executive Mark Goldwater said the study was "fundamentally flawed" and claimed it had used prices from "one-off special offers" in mainstream supermarkets.

Mr Tricot said the comparisons between kosher prices and supermarkets were "entirely reasonable" and said special offers had been excluded from the study.