The Game of Thrones actor Lena Headey has spoken of how she felt “powerless” during an encounter with Harvey Weinstein, adding her voice to the growing number of women who have accused the producer of sexual misconduct.

In a series of posts on Twitter, Headey said that Weinstein had spoken to her inappropriately at the Venice film festival and reacted with anger when she resisted his advances in a Los Angeles hotel.

Headey says that the first encounter with Weinstein, in Venice, came when she was promoting The Brothers Grimm, which was being distributed by the producer’s company, Miramax. “At one point Harvey asked me to take a walk down to the water, I walked down with him and he stopped and made some suggestive comment, a gesture. I just laughed it off, I was genuinely shocked,” she wrote.

A second encounter came after a breakfast meeting with the producer in an LA hotel, which Headey assumed would be about potential work. Headey says that Weinstein began asking questions about her love life and later invited her to his room to look at a script.

“We walked to the lift and the energy shifted, my whole body went into high alert, the lift was going up and I said to Harvey, ‘I’m not interested in anything other than work, please don’t think I got in here with you for any other reason, nothing is going to happen,’” she wrote.

Headey said that Weinstein was “furious” and marched her to his room with his hand on her back. “I felt completely powerless,” she added. When Weinstein’s key card to his hotel room did not work, he walked her to the hotel exit “by grabbing and holding tightly to the back of my arm”.

As Headey was leaving the hotel, Weinstein allegedly whispered: “Don’t tell anybody about this. Not your manager, not your agent.”

“I got into my car and I cried,” the actor added.

Headey’s account comes after more than 40 other women have accused Weinstein of sexual assault and harassment following the publication of investigations by the New York Times and the New Yorker. Following the revelations, Weinstein was sacked by the board of his company and expelled from the Academy of Motion Picture Arts and Sciences. On Monday the actor Lauren Holly also came forward with claims against Weinstein, describing an encounter she had with the producer in a hotel in the 1990s in which he asked her for a massage while naked. “I wanted to flee. I was scared,” Holly told Canadian talk show The Social.

Weinstein has “unequivocally denied” all allegations of non-consensual sex. “With respect to any women who have made allegations on the record, Mr Weinstein believes that all of these relationships were consensual,” a spokesperson for the producer said.