The grand rabbi of a Brooklyn-based Orthodox Jewish group and five other men accused in a tax fraud and money laundering scheme pleaded not guilty to federal charges on Monday.

Grand Rabbi Naftali Tzi Weisz, head of the Spinka religious group, and his executive assistant, Gabbai Moseh E. Zigelman, are accused of soliciting “tens of millions of dollars” in contributions to Spinka charities while secretly promising to refund up to 95% of contributors’ donations, federal prosecutors said. The contributors then illegally claimed tax deductions on their bogus donations.