A Rikers inmate is suing the city for $25 million, saying guards forced an object up his rectum as retaliation for the attempted rape of a female colleague — even though another prisoner was indicted for the attack the previous day.

Inmate Anthony McNeil, who’s awaiting trial on charges of robbing a 78-year-old woman, says he was repeatedly refused medical attention until he was finally admitted to Bellevue three days later.

A Department of Correction spokeswoman said, “We are investigating these allegations. DOC is fully committed to protecting the safety of all inmates in city custody.”