Former radio talk show host Gregg T. Rennie pleaded guilty in US District Court in Boston to charges related to a multimillion-dollar Ponzi scheme, and now faces up to up to 20 years in prison on each of 13 counts of securities fraud and one count of wire fraud.

Prosecutors said the 44-year-old Quincy resident stole at least $3.2 million from victims, including elderly retirees, a church congregation saving for a new building, and listeners of his radio show, “Your Money.’’

Rennie told investors he could offer a guaranteed rate of return in risk-free federal housing certificates and annuities. But instead of investing the money, he used it to fund his expenses, prosecutors said. To conceal the fraud, Rennie made periodic payments to some victims, showed them prospectuses, and sent victims bogus invoices.