A UK-based pensioner accused of being a Nazi war criminal cannot be prosecuted due to insufficient evidence, police have said.

The Guardian newspaper reported that Alexander Schweidler - now living in a Milton Keynes housing estate - was involved in atrocities at the Mathausen camp in Austria where more than 80,000 people were murdered.

It said Mr Schweidler has been a naturalised British citizen since 1964, and is drawing a full state pension.

The Metropolitan Police say a man was interviewed in 1996 in connection with specific allegations, attending a police station with his solicitor, but was not arrested.

Further enquiries were made, which included officers travelling to Austria, and a report was sent to the Crown Prosecution Service. The CPs decided there was insufficient evidence to give a realistic chance of a conviction.

Mr Schweidler, 78, was informed in 1997 that no further action would be taken against him.

But despite the police statement, the head of the Holocaust Educational Trust said he had evidence - in the form of a judgment from a US court - that the pensioner was involved in wartime atrocities.

Head of the Holocaust Educational Trust Lord Janner said he wanted an "immediate inquiry" opened and said a reconstituted meeting of the Parliamentary War Crimes Group would be discussing the case on Thursday afternoon.

Lord Janner said the US Department of Justice had investigated the pensioner, and decided he should be "deported because he was a war criminal".

"Mathausen was a revolting, awful concentration camp... to me it would be revolting to have living next door someone who was a guard at that camp," he said.

The accusations follow the recent controversy surrounding alleged Nazi death squad officer Konrad Kalejs, who fled the UK earlier this month.

Lord Janner said: "The difference is that in the case of Kalejs the home secretary had no alternative other than to let him out, except what he did do which was to order that if he didn't go voluntarily he should be deported.

"They [the police] had not got time to investigate. Here they have."