The I Am Robot star was sued for at least $20 million (£14 million) by his actor dad Thomas Knight Slater, who goes by the stage name Michael Hawkins, for defamation in February (16) for suggesting he was battling "manic-depressive schizophrenia" in a 2015 interview.

Thomas, 80, claims Christian's comments have caused him to be blacklisted from Hollywood and he is struggling to find work due to the mental health allegations.

Christian has now responded with his own legal documents, in which he reportedly claims his mother Mary Jo told him about Thomas' schizophrenia diagnosis and informed him Thomas was taken to hospital in 1972 for threatening to harm her and Christian.

The 46-year-old, who claims his father hasn't worked since 1988 due to his condition, also submitted "rambling" postcards written by his father, according to TMZ.com. He wants a judge to throw out the lawsuit.

Thomas, who was married to Mary Jo between 1966 and 1976, enjoyed roles in soap operas including Ryan's Hope and As the World Turns, and he had parts in films like The Amityville Horror, Midnight Run and Mommie Dearest. He also acted under the name Michael Gainsborough.