Accused child-killer Casey Anthony paid her lawyer with sex, according to a report Tuesday.

A private investigator hired by Casey’s lawyer, Jose Baez, in her murder case claimed that he learned that Anthony was trading sex for legal representation after a TV show requested an interview with her that she didn’t want to do in 2008, according to the gossip website RadarOnline.

“[Baez] called the network saying they would have to take a raincheck, hung up the phone and said to Casey: ‘You now owe me three blowjobs,’ ” according to PI Dominic Casey, who Radar says gave the sworn testimony in January as part of a bankruptcy case.

The alleged shenanigans got worse as time went by because Anthony was broke, the private detective claims.

“The misconduct between Casey and Jose escalated,” the PI said, adding that he once “witnessed a naked Casey’’ run from Baez’s private chambers.

“That night, I told her that she cannot allow him to continue engaging in this behavior. … Casey told me she had to do what Jose said because she had no money for her defense,’’ the private detective said, according to an affidavit obtained by the celebrity news website.

In 2011, Anthony was found not guilty of murdering her 2-year-old daughter, Caylee.

Baez declined to comment.