The father of disgraced US lobbyist Jack Abramoff said George Clooney's Golden Globes speech made a "ridiculous attack" on his son, reports have said.
Clooney joked about Jack Abramoff's name in his speech
Trade paper Variety said it received an open letter from Frank Abramoff saying Clooney's words were "deeply hurtful".
Clooney said on Monday: "Who would name their kid 'Jack' with 'off' at the end? No wonder the guy's screwed up."
Jack Abramoff pleaded guilty earlier this month to corruption charges. Clooney was unavailable for comment.
Clooney won a Golden Globe for best supporting actor for his role in political drama Syriana, which focuses on the murky world of US foreign policy and the oil industry.
Jack Abramoff is accused over a business deal in 2000
He plays a disillusioned CIA agent who becomes a scapegoat when an operation in the Middle East goes awry.
His comments during his speech raised a large laugh from the Golden Globes audience.
According to Variety, Frank Abramoff wrote to Clooney: "Your glib and ridiculous attack on my son, Jack, coupled with your obscene query as to the choice his mother and I made in naming him brought shame and dishonour on you and your profession.
"What drove you to this lapse in lucidity, I can never know, but you need to know that your words were deeply hurtful to many innocent and decent people."
He said the lobbyist's daughter, who was watching the show, was in "a fit of tears".
Clooney's Bafta success
Abramoff is currently co-operating with a probe into alleged corruption among US Congress members, having accepted the terms of a plea bargain.
Under the corruption charges he faces, Abramoff was accused of using gifts of money, foreign trips and lavish meals to buy political influence.
Clooney was shortlisted on Thursday for four Bafta nominations, including best director, supporting actor and screenwriter for Good Night, and Good Luck, a film about Edward R Murrow and the early days of broadcast journalism in 1950s America.
He is also up for best supporting actor for Syriana.