Noel Clarke's Kidulthood co-star Adam Deacon has alleged he was a victim of the actor for 15 years, saying the star sabotaged his career and that his "gaslighting" led to "the complete breakdown" of his mental health.
Deacon made the claims in a statement saying he believes "every single word" of the allegations made by more than 20 women accusing Clarke of misconduct.
In response to the original claims, first published following an investigation by the Guardian newspaper, Clarke "vehemently" denied allegations of sexual misconduct and criminal behaviour but apologised "deeply" for his actions and said he would be seeking professional help.
Deacon starred in Clarke's gritty break-out film Kidulthood in 2006 and the 2008 follow-up Adulthood, but the pair have a complicated history. After a public fall-out, Deacon was given a restraining order in 2015 after being convicted of harassing his former mentor.
However, Deacon says it was Clarke's "sociopathic" behaviour that led to his breakdown and that those with mental health problems "should still be believed".
Posting his statement on Twitter, Deacon said: "I would like to start by saying that I stand by all the women who have spoken out and told of their harrowing experiences with Noel Clarke. I wholeheartedly believe every single word and I hope that anyone who is yet to come forward with information will be listened to.
"I myself have been a victim of Noel Clarke for 15 years. My career was continually sabotaged and the gaslighting became so severe that it led to the complete breakdown of my mental health.
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"As you will know I have spoken out regarding this man's sociopathic behaviour on multiple occasions but my claims were always dismissed. People dealing with mental health may at times explain things differently but they should still be believed."
Deacon went on to say he wished his claims had been believed earlier.
"I only wish that everyone had taken more notice of my words," he said. "[Clarke's] horrific abuse of power could have been stopped before it affected so many others."
During 2020, Deacon suffered another breakdown, and wrote about his experiences for Sky News.
Like Clarke, he was a recipient of BAFTA's rising star award, picking up the prize in 2012, three years after his former mentor.
Despite winning the award ahead of the likes of Eddie Redmayne, Tom Hiddleston, Chris Hemsworth and Chris O'Dowd, his career never really took off as it did for other winners, including James McAvoy, Kristen Stewart and Daniel Kaluuya, as well as Clarke.
However, Deacon has started working again more recently, with films including Rogue, alongside Megan Fox, and Original Gangster, starring Steve Guttenberg, released in 2020.
He said in his statement that he was thankful for support received since the allegations against Clarke were first published, and added that he was concentrating on his acting career.
He continued: "While recent events have served as a small vindication for me I am beyond saddened by the pain that so many people have had to endure at the hands of Noel Clarke.
"I am now looking forward to a fresh start and focussing all my time and energy on my acting career."
Clarke, 45, has over the last 15 years established himself as one of the British film industry's most prominent success stories.
He won critical acclaim for Kidulthood and Adulthood and went on to find mainstream success in one of the country's best-loved series, with a role in Doctor Who between 2005 and 2010.
In April, he was given BAFTA's prestigious outstanding British contribution to cinema award – since taken away following the allegations.
The Met Police force has said it has received a third-party report relating to claims of sexual offences committed by a male, but there is no investigation under way.
A representative for Clarke declined to comment on Deacon's statement.