An eminent Canadian historian whose writings on the Holocaust in Poland have attracted death threats said Tuesday that fierce criticism of his research is an unjustified attack on academic freedom.

In an interview, University of Ottawa Prof. Jan Grabowski, 55, said he would not allow the "campaign of hate" to distract him from delving into what he called an ugly, but little-told, piece of history.

"I feel personally attacked but this is for me a much more dangerous and general problem that has to be dealt with," Grabowski told The Canadian Press from Ottawa. "It's a pure and simple attack on basic academic freedoms, which we take for granted here in Canada. I'm dismayed."

The history professor, who has spent years studying the Holocaust in Poland, maintains many Poles who killed Jews were not simply forced to collaborate with the Nazis, who occupied the country during the Second World War.

'Nothing is simple here'

"They were realizing their own dream of a Jew-free Poland," Grabowski said. "At the same time, they were very ardent opponents of the German occupation. Nothing is simple here."

While no stranger to controversy over his views, what's changed recently is that his critics are no longer content to denounce him in Poland. Now, he said, they have brought their criticism to Canada by writing directly to the university where he has worked for almost 25 years to accuse him of lying and fabricating historical evidence.

In two letters this month, the Polish League Against Defamation says Grabowski's views are damaging to Poland.

"He falsifies the history of Poland, proclaiming the thesis that Poles are complicit in the extermination of Jews," the league writes. "Grabowski fails to adhere to the fundamental rules of researcher's credibility. He uses vivid and exaggerated statements to create propagandistic constructions, rather than to provide an honest picture."

One of the letters is signed by 130 Polish scholars — none, he says, with any connection to Holocaust studies.

Political climate emboldening critics

In 2014, Grabowski was given the Yad Vashem International Book Prize for his work Hunt for the Jews: Betrayal and Murder in German-Occupied Poland, an award the league called "disturbing."

Grabowski said the prevailing political climate in eastern Europe is emboldening nationalist groups. He also said some of the league's founders are now either ranking members of Poland's government or senior advisers to its ministers.

"It's to an extent aligned with the wishes of the Polish state, which makes it all the more, I would say, appalling," he said of the group's campaign.

In a display of solidarity, however, scores of pre-eminent international Holocaust scholars on Monday penned a letter to the chancellor of the University of Ottawa defending Grabowski as a scholar of "impeccable personal and professional integrity."

We are confident that your university, which is a bastion of learning and freedom of scholarly inquiry, will give its full support to Prof. Grabowski. - Letter supporting Jan Grabowski

The letter praises his courage in pursuing his research despite the attempts to shut him down. The writers also criticize the league.

"The current attack on Prof. Grabowski by the Polish League Against Defamation, as in a recent public letter signed by more than 100 academics who have no expertise in the subject, is baseless, putting forth a distorted and whitewashed version of the history of Poland during the Holocaust era," the letter states.

"We are confident that your university, which is a bastion of learning and freedom of scholarly inquiry, will give its full

support to Prof. Grabowski against those who seek to besmirch his reputation and curtail his work, and by extension, ours as well."

Grabowski said the University of Ottawa, seen here, has offered him its full support. (Danny Globerman/CBC)

League denies campaign

League founder Maciej Swirski denied in an email on Tuesday that it was running a campaign targeting Grabowski or academic freedom.

"This is to pay attention to the campaign of slander against Poland conducted by Mr. Grabowski," Swirski said.

About 5.5 million Polish citizens — three million of them Jews — were killed in the war and many Poles view their nation as blameless in an era of Nazi atrocities.

Grabowski, who was due to fly to Warsaw on Wednesday to continue his research, said his work uncovered grim truths about that view.

"What I found is huge areas of human misery that has not been reported sufficiently or never," he said. "These things are not palatable to Polish nationalists who believe in myths."

The professor said he had reported the threats to authorities and was exploring his legal options.

The University of Ottawa did not responded immediately to a request for comment but the professor said the rector assured him of its full support.