An ex-boyfriend of Christine Blasey Ford reportedly wrote a letter to the Senate Judiciary Committee contradicting her testimony last Thursday on polygraphs — prompting Sen. Chuck Grassley to raise doubts about her truthfulness.

The man, who says he dated Ford from 1992 to 1998, wrote in the letter — obtained by Fox News — that he once saw Ford help ease the nerves of a friend preparing to take a polygraph by ­“explaining in detail what to ­expect” and how they work.

During last Thursday’s hearing, Arizona sex crimes prosecutor Rachel Mitchell asked Ford if she had ever talked with anyone other than her lawyers about “how to take a polygraph.” Ford said, “Never.”

The man, whose name was not released, also said that during his relationship with Ford, she never mentioned Brett Kavanaugh or her experience as a victim of sexual assault.

In a letter late Tuesday, Grassley (R-Iowa) asked Ford’s lawyers for the polygraph results, saying the ex’s claim “raises specific concerns about the reliability of [Ford’s] polygraph-examination results.”