WARSAW, Poland (JTA) — A Polish-Canadian Holocaust researcher has sued a Polish organization after it accused him publicly of ruining Poland’s good name and charging that his research falsifies the nation’s history.

Jan Grabowski, a professor at the University of Ottawa, filed the lawsuit Thursday against the Polish League Against Defamation in Warsaw District Court.

The suit proposes that each person who signed a Polish League statement condemning Grabowski published in June 2017 purchase and donate to one Polish high school a copy of the book “Night Without an End: Fate of Jews in selected counties of occupied Poland.”

The statement was signed by 134 people and circulated, among others, to authorities at the University of Ottawa. The suit claims that it was in this document that the libelous statements were made.

Lawyers representing the historian say that the letter called into question confidence Grabowski’s scientific reliability and knowledge, and that “the goal of the organization was to discredit him in the eyes of the scientific community.”

The Polish League’s statement pointed to the professor’s allegedly “slanderous and unfavorable attitude towards Poland and Poles,” expressed through his publishing of results of his research into the Holocaust and the crimes committed by Poles against Jews during World War II. The statement suggested that Grabowski’s research is anti-Polish, which the organization said violates not only his academic reputation but also his national pride.

According to the Polish League statement “Grabowski does not follow the basic principles of researcher reliability,” “builds propaganda constructions,” “eliminates key facts” and “[his work] has nothing to do with professional research.”

Grabowski said that among the signers, there was no professional dealing with the history of the Holocaust.

The Polish League says it aims to “straighten out false information about Polish history.” Its president is Maciej Swirski, until recently the vice president of the Polish National Foundation founded by Poland’s right-wing government.

Grabowski is a co-founder of the Center for Holocaust Research in Warsaw, and author and editor of numerous publications about the Holocaust. In 2014, his book “Hunt for the Jews” received the Yad Vashem International Book Prize for Holocaust Research.