Sean McCray, who also sued the Senate Democratic Caucus, was a grand jury witness in an investigation by the state Attorney General's Office that resulted in Washington being charged with two felonies on March 12.
McCray repeats in his lawsuit, filed Friday in Montgomery County, the raging response he said Washington gave when he repeatedly told her to stop using state tax dollars to fund an annual political fundraiser that doubled as her lavish birthday party.
"I am the f------ Senator, I do what the f--- I want, how I want, and ain't nobody going to change me," McCray said she told him.
McCray also accuses Washington of ordering him to not hire a woman because she was a lesbian and of making "homophobic comments" about employees.
Washington's defense attorney, Henry Hockeimer Jr., yesterday said he had not seen McCray's lawsuit and declined to comment about its contents.
Hockeimer, responding to investigators searching Washington's offices in October, described the state probe as a "matter apparently triggered by a disgruntled former employee who was terminated earlier this year."
McCray's lawsuit accuses Washington of "humiliation, embarrassment and ill treatment" that caused him to become "increasingly depressed and physically ill," needing treatment.
He accuses Robert Kline, director of administration for the Senate Democratic Caucus, of falsely accusing him of being "disrespectful and violent" in the office.
Stacey Witalec, a spokeswoman for the Democratic Caucus, declined to comment yesterday.
Washington, 68, of Cheltenham, has served in the Senate since 2005. She served in the state House from 1993 to 2005.
Washington faces Brian Gralnick and Art Haywood, both of Cheltenham, in today's Democratic primary election.
Republican Robin Gilchrist, also of Cheltenham, is unopposed in his primary election today.
The 4th District covers parts of Philadelphia and Montgomery County.
On Twitter: @ChrisBrennanDN