George Clooney has said he had "no idea" that his former ER co-star Vanessa Marquez was "blacklisted", adding he had no say in the casting of the show.

Marquez had claimed she was sexually and racially harassed daily on set and that Clooney helped "blacklist" her for reporting the matter. Responding to her accusations, Clooney told E! News: "I had no idea Vanessa was blacklisted. I take her at her word. I was not a writer or a producer or a director on that show. I had nothing to do with casting. I was an actor and only an actor."

The 56-year-old Hollywood star insisted that he wasn't involved in any decision about her career.

"If she was told I was involved in any decision about her career then she was lied to. The fact that I couldn't affect her career is only surpassed by the fact that I wouldn't," he explained to the publication.

Clooney played Dr Doug Ross on the NBC medical drama from 1994 to 1999, in which Marquez starred as nurse Wendy Goldman in the first three seasons.

Previously, Marquez retweeted an article in which Clooney spoke out against Harvey Weinstein's sexual misconduct allegations. She wrote: "B.S.Clooney helped blacklist me when I spoke up abt harassment on ER. 'Women who don't play the game lose career'I did."

In a series of tweets, she also claimed she was "racially and sexually harassed on set daily".

Meanwhile, Clooney, who worked closely with Weinstein on several films, said he was shocked by the harassment claims that have come out this week.

Clooney said in an interview with The Daily Beast: "It's indefensible. That's the only word you can start with. Harvey's admitted to it, and it's indefensible."

He continued: "I've known Harvey for 20 years. He gave me my first big break as an actor in films on From Dusk till Dawn, he gave me my first big break as a director with Confessions of a Dangerous Mind. We've had dinners, we've been on location together, we've had arguments. But I can tell you that I've never seen any of this behaviour — ever."