Europe's largest kosher-food manufacturer this week admitted that a chicken schnitzel which made a meals-on-wheels customer ill had been undercooked.

Hermolis said it had now put in place new procedures after Simone Simmons, 52, from Hendon, North-West London, was supplied the schnitzel which she said had made her sick.

Michael Lisser, managing director of the Wembley-based firm, said: "We used to probe [temperature check] one in every three to five schnitzels after cooking a batch to make sure they were hot enough and thoroughly cooked.

"On this occasion, there must have been one schnitzel that was thicker than all the others and so didn't cook fully in the centre. The other 13 schnitzels in that batch were all fine."

He added that Hermolis, which provides kosher meals for the meals-on-wheels services of several councils, as well as airlines hotels and hospitals, had implemented new procedures.

"We will now probe every single schnitzel after it is cooked. This was a very unusual case. We are constantly audited and have always passed with flying colours and nothing like this has ever happened before, but we have taken the necessary action."

Ms Simmons receives kosher meals-on-wheels from Barnet council, who buy them from Hermolis. She told a local newspaper: "I ate some of [it]... at 1pm and by 5pm I was vomiting.

"When I looked at the meat, I saw the inside of it was completely raw. I'm mainly concerned about older people, who may have bad eyesight and not be able to see properly."

A spokesman for Barnet Council, which is jointly investigating the issue with Enfield Council, with which it shares the meals-on-wheels contract, said: "Environmental-health officers from Barnet took a sample of the meat and confirmed that it did appear to be undercooked and this information was passed on to environmental health officers in Brent, where the production premises are located.

"The council is committed to all recipients of meals at home, including our Jewish customers, receiving a high level of service as part of our commitment to supporting the vulnerable."