Russell Brand has denied "very serious criminal allegations" that he claims will be made against him by a newspaper and TV company.
In a video posted on YouTube and X, formerly known as Twitter, titled "So, This is Happening", the comedian denied the allegations that he described as "a litany of extremely egregious and aggressive attacks".
He said that while he was "very promiscuous" at the height of his career, his relationships were "always consensual".
It comes ahead of a special programme by Channel 4's Dispatches which is set to air on Saturday night, and which Sky News understands will feature the yet unspecified allegations.
A report by The Sunday Times newspaper is also set to be published overnight.
Brand, 48, said: "Now, this isn't the usual type of video we make on this channel where we critique, attack and undermine the news in all its corruption because in this story, I am the news.
'Very serious allegations that I absolutely refute'
"I've received two extremely disturbing letters or a letter and an email. One from a mainstream media TV company, one from a newspaper listing a litany of extremely egregious and aggressive attacks, as well as some pretty stupid stuff like my community festival should be stopped, that I shouldn't be able to attack mainstream media narratives on this channel.
"But amidst this litany of astonishing rather baroque attacks, are some very serious allegations that I absolutely refute.
"These allegations pertain to the time when I was working in the mainstream, when I was in the newspapers all the time, when I was in the movies. And as I've written about extensively in my books, I was very, very promiscuous.
"Now, during that time of promiscuity, the relationships I had were absolutely always consensual. I was always transparent about that then, almost too transparent, and I'm being transparent about it now as well.
"And to see that transparency metastasized into something criminal that I absolutely deny makes me question, is there another agenda at play?"
He continued: "I'm aware that you guys have been saying in the comments for a while [saying] 'watch out, Russell. They're coming for you, you're getting too close to the truth, Russell Brand did not kill himself'.
"I know that a year ago there was a spate of articles - Russell Brand's a conspiracy theorist, Russell Brand's right wing. I'm aware of news media making phone calls, sending letters to people I know for ages and ages.
'A serious and concerted agenda'
"It's being clear to me, or at least it feels to me like there's a serious and concerted agenda to control these kind of spaces and these kind of voices. And I mean, my voice along with your voice.
"I don't mind them using my books and my stand-up to talk about my promiscuous consensual conduct in the past. What I seriously refute are these very, very serious criminal allegations.
"Also, it's worth mentioning that there are witnesses whose evidence directly contradicts the narrative that these two mainstream media outlets are trying to construct, apparently, in what seems to me to be a coordinated attack.
"Now, I don't wanna get into this any further because of the serious nature of the allegations, but I feel like I'm being attacked and plainly they're working very closely together. We are obviously going to look into this matter 'cause it's very, very serious. In the meantime, I want you to stay close, stay awake, but more important than any of that, if you can, please stay free."
Brand has not named the newspaper and TV company which he claims have made allegations against him.