Asked if a photographer can take a few shots, Dr Efraim Zuroff grins.

"So long as it's just pictures. There are people who want to take other kinds of shots at me," he says.

Being a Nazi-hunter is clearly not an easy business. Many a threat has been thrown Mr Zuroff's way in the course of his work to bring Nazi war criminals to justice.

In his new book, Operation Last Chance, the 61-year-old details much of the work he has done in both seeking out former Nazis in hiding since the end of World War II and, more commonly, battling with governments reluctant to dredge up a past made embarrassing by the actions of its citizens, who, far from being in hiding, were listed in their local phone book.

He has performed these tasks as head of the Jerusalem office of the Simon Wiesenthal Center, whose Operation Last Chance is a final push to bring prosecutions against former Nazis before they die.

"Among other things, I wanted to expose in my book the fact that the biggest obstacle today to prosecution of Nazi war criminals is not necessarily finding them, or their age - although that's obviously a problem - but lack of political will," Mr Zuroff says.

To make the point, he compares a serial killer with a war criminal. The former, he says, is an immediate threat to the public and will be pursued by the authorities, but the latter will probably have led a law-abiding life ever since the end of the war and will therefore pose no threat to anyone. And so they will be left alone.

"Governments understand that all they have to do is wait it out, wait a couple of years, the people will die and the problem will be over. It's a combination of self-interest, anti-Semitism and a lack of political courage."

Mr Zuroff's office publishes an annual report naming the "most wanted" among the world's surviving Nazi criminal suspects. But this year's report could be the last.

"One of the main reasons behind this report is to focus on the failure of certain governments to bring Nazis to justice," he says.

"If the report can no longer help in a practical sense..." He tails off and seems a little coy. "Look, it might go on to 2013, I'm not sure."

And will the end of the reports coincide with Mr Zuroff's retirement?

"It could well mark the end."

A husband, father and grandfather, Mr Zuroff hints at a toll on his personal life, explaining how two of his grandchildren were born while he was either away or busy arranging bounties for wanted Nazis.

But he is keen to stress that his work and that of his organisation is not about to stop just yet, and how another reason for writing a book about Nazi hunting is because "the issue is not dead yet".

He recalls seeking advice from the US Office of Special Investigations, which de-naturalises and deports war criminals in America, as to whether he should accept the offer of a job looking for Nazis full-time.

"How much longer will this last?" Mr Zuroff had asked, referring to the search for Nazis. "Three to five years," was the reply. This was in 1981.

And he points out how in 1989 a book about the case of Josef Schwammberger, the former labour camp commander convicted of murder, was given the somewhat premature title of The Last Nazi.

"We now have Holocaust Memorial Day, the 65th anniversary of the liberation of Auschwitz, and nine months ago there were at least 706 ongoing investigations in 12 countries.

"Not even 10% will reach trial, but this means there is a lot that's going on."

Mr Zuroff is also keen to mention the trials of suspected Nazis John Demjanjuk and Heinrich Boere in Germany, plus other ongoing indictments in that country.

"It's amazing what's going on in Germany now," he says.

Within a decade all of those under suspicion for World War II crimes will probably be dead.

Therefore, Mr Zuroff says, the future for his Jerusalem office lies in preserving the historical accuracy of the memory of the Holocaust and education about its atrocities.

"I sometimes say to myself that the real title, the real name that I should have is not Nazi hunter, but truth warrior, because we're fighting for the truth, and the truth is in danger. We have to ensure that the accuracy of the historical record about the Holocaust is preserved, and fight anti-Semitism."

Mr Zuroff does say he wishes he had been more successful in bringing Nazis to justice, but that "we did some amazing things in terms of focusing attention on Nazi criminals" and in explaining how "it wasn't Germany and Austria against the Jews, it was Europe against the Jews".

But, he adds: "Perhaps if we had focused more intently on individual cases maybe more of those people would have been brought to justice, but we just didn't have the money.

"How can you compare the resources of an NGO like the Simon Wiesenthal Center with the resources of a government? It's not our obligation, it was governments that screwed up."

In life, as in the pursuance of war criminals, there is often one who got away. For Mr Zuroff it is Aribert Heim, the doctor accused of sadistic experiments on prisoners at the Nazis' Mauthausen concentration camp in Austria.

He is now thought to have died in Egypt in 1992, and although Mr Zuroff remains sceptical of this, he concedes Heim is unlikely ever to be caught.

"It would have been one of the most important trials in the last 30 years. It would have been the crowing achievement. It would have been a real coup," he says wistfully.

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