A man entrusted to give talks at Polish schools about Judaism and lead Jewish prayers was neither a rabbi nor even Jewish, media reports say.
The man who called himself Jacoob Ben Nistell from Haifa in Israel was in fact a Catholic cook named Jacek Niszczota, the reports say.
The bearded man with sidelocks and wide-brimmed hat has now disappeared from the Polish city of Poznan.
But the small Jewish community there has still thanked him for his help.
Newspaper Glos Wielkopolski uncovered the apparent deception (in Polish) after the “rabbi” was interviewed on TV.
Someone from his hometown, Ciechanow in central Poland, had recognised him.
He then disappeared and could not be contacted again, the paper said.
Alicja Kobus, president of Poznan’s Jewish community, told Agence France-Presse that no-one had thought to check the rabbi’s identity.
“I admire his determination – he had learnt Hebrew, the Jewish traditions and prayers, all through listening to Israeli radio,” she said.
She bore him no ill will, she added, as he had never accepted a single zloty for his work with the community.
His dark beard and sidelocks must have been dyed, she said, as they later found out that Jacek Niszczota was in fact blond.