William Shatner -- Sued for Allegedly Harassing the Help

William Shatner purposely "harassed and berated" a former employee ... all because the employee refused to sign a waiver after getting injured on the job -- this according to new legal docs.

Oscar Alfaro and his wife Delmy filed a lawsuit in L.A. County Superior court today -- claiming they both worked for Shatner for twenty years. He was a handyman. She was a housekeeper.

In the docs, Oscar claims he was injured while working at the actor's Studio City home ... but when Shatner wanted him to sign a document to release him from financial responsibility ... Oscar refused.

Oscar claims that as a result of his refusal ... the actor and his wife retaliated against him by harassing Oscar and his wife to the point where they were both forced to quit their jobs.

Oscar and his wife claim they suffered humiliation, embarrassment, and mental anguish in addition to the loss of earnings.