Braun was summoned to IPN's Kraków office on Tuesday, where prosecutors from the institute's dedicated commission informed him of the charge.
He did not plead guilty, but did not retract his earlier comments either.
Prosecutors allege that in July 2025, in the towns of Jedwabne and Warsaw, Braun publicly questioned the existence of gas chambers at the former German Nazi concentration and extermination camp of Auschwitz-Birkenau, and their use for the mass killing of prisoners.
The remarks were made in interviews on Radio Wnet and on a YouTube programme, in which Braun said: "Gas chambers are unfortunately fake, but ritual murder is a fact."
The IPN said the claims contradict well-established historical knowledge based on documents, witness testimony, perpetrators' own admissions and criminal investigations, both past and ongoing.
It added that traces of hydrogen cyanide in the remains of the camp's mass-killing apparatus were confirmed by scientific studies carried out in the 1990s by the Kraków-based Institute of Forensic Research.
"Ritual murder" is a fake, libelous claim that has been used for centuries by antisemites to inflame anti-Jewish sentiments.
Prosecutors have focused specifically on the gas chamber remark.
Speaking to supporters gathered outside IPN's Krakow office, Braun said: "They try to blackmail the public by saying these are universally known and unquestionable facts."
Among those outside the building was Mateusz Piskorski, a politician known for his pro-Russian views.
The charge follows the European Parliament's decision to lift Braun's parliamentary immunity, after prosecutors opened an investigation in July last year based on complaints from Left party MP Anna-Maria Żukowska, Auschwitz-Birkenau State Museum director Piotr Cywiński and Bartosz Staszewski of the Basta Foundation.
Denying Nazi crimes is a criminal offence in Poland under the IPN Act, punishable by a fine or up to three years in prison.
Auschwitz-Birkenau was the largest Nazi German concentration and extermination camp in occupied Poland.
More than 1.1 million people, mostly Jews, were murdered there during World War II.
(ał)
Source: PAP, polsatnews.pl