A new case of a former Nazi concentration camp guard believed to be living in Britain is being investigated by the Israel office of the Simon Wiesenthal Centre.

The Centre’s director, Dr Efraim Zuroff, said the man, whom he would not identify, had been a guard at two camps where Jews were murdered.

Dr Zuroff said: “We know he is alive, we know where he is and we know what he did. Apparently, he was punished for part of what he did,but not all. Now we have been looking into the possibility that he was at two different camps. We believe he was punished for his role in one camp but not the other.”

The veteran Nazi-hunter said he and his colleagues were investigating whether or not the man was directly involved in the killing of Jews. “Jews were killed in both camps,” he said.

Dr Zuroff said it was believed the man had served a sentence for offences at the first camp, but would not say whether he had served a jail term or some other form of punishment. He was guarded about releasing anything other than the barest information about the case, saying he feared there was a danger that the man would flee.

The Centre has also begun investigating whether the man could be prosecuted for any actions at the second camp and how he came to be in Britain.

News of the case has come as the trial of John Demjanjuk continues in Munich, Germany. Ukranian-born car worker Demjanjuk, 89, has been accused of being an accessory to the murder of 29,700 Jews while he was allegedly a guard at the Sobibor concentration camp in Poland in 1943. He denies the charge.