The suspected Nazi war criminal Konrad Kalejs may yet face prosecution as Latvian authorities re-open their investigations into claims he committed mass murder during World War II.

The UK authorities have already started deportation proceedings against the 86-year-old Latvian-born Australian citizen, because the police did not have enough evidence to arrest him.

But Scotland Yard is continuing its investigations into claims that Mr Kalejs took part in war crimes against mainly Jewish civilians.

Mr Kalejs is expected to leave the UK by Thursday of his own free will, and return to Australia.

But the Latvian authorities have said this would not affect their attempts to seek his extradition should fresh evidence be revealed.

Speaking after a meeting with the Latvian ambassador in London the head of the Holocaust Education Trust, Lord Janner detailed the action being taken by the Latvian authorities.

He told the BBC they are "re-interviewing the witnesses, they are looking at all the evidence again, and they are seeking new evidence and if they get sufficient to warrant a prosecution they will seek extradition."

Lord Janner, added: "It does not matter where this man seeks to go on the face of the globe they will seek to extradite him."

The campaigner for the trial of those alleged to have committed atrocities during the war also discussed the issue with the Home Secretary Jack Straw earlier on Tuesday.

'No admissible evidence' - Straw

Mr Straw told him the decision whether to arrest Mr Kalejs rested with the police.

In a statement issued after the meeting Mr Straw said the police simply did not have enough evidence to warrant an arrest.

Mr Straw defended his decision to begin the deportation of Mr Kalejs as his presence in Britain was "not conducive to the public good".

"It is not open to me, as home secretary, or to the police to prevent any individual from leaving the UK unless they are the subject of criminal charges," he said.

But the decision not to put Mr Kalejs on trial in the UK has attracted criticism from abroad.

Some of the evidence sent to the UK authorities investigating Mr Kalejs was collected from witnesses by the Simon Wiesenthal Centre in Jerusalem.

That evidence was also presented at a US Justice Department hearing in 1993 and persuaded one official to conclude that Mr Kalejs was second in command of one of the most notorious mass killing units of World War II.

Straw 'took easy way out'

Dr Efraim Zuroff, head of the Wiesenthal Centre, said governments preferred not to deal with the issue.

He said: "In Britain, Home Secretary Straw took the easy way out by simply throwing away the hot potato."

On Tuesday, shadow home secretary Ann Widdecombe repeated her call for Mr Straw to issue a public statement about his decision.

She said: "It would be a real betrayal of justice and human rights if Konrad Kalejs were to be prematurely deported and then new evidence were to be uncovered."

Mr Kalejs arrived in Britain six months ago after being deported from Canada and the US and has been staying at Catthorpe Manor, Lutterworth, a retirement home run by the Latvian Welfare Fund.

Few witnesses

The pensioner, who says he spent the war as a student and a farm labourer, has dismissed his accusers as "liars and storytellers".

But one survivor of the Salas-pils concentration camp, Alfred Winter, is adamant that it would have been nearly impossible for someone like Konrad Kalejs, who was part of the Arayas commando not to have been involved in crimes against humanity.

While the director of the United States Justice Department's office of special investigations, Eli Rosenbaum says he is sure that Mr Kalejs is guilty.

He told the BBC: "He is a major perpetrator of Nazi crimes during the Second World War."

But he added that it was possible that Mr Kalejs may have outlived any witnesses to his crimes.