ITV News and the Guardian have published reports alleging that David Walliams has been accused of sexual misconduct by several women, including one who was aged 15.

The allegations were made as a part of a joint three-year investigation, external by the two news organisations, which was published after the entertainer lost a legal bid to stop the claims against him being made public.

Some of the women accuse Walliams of “grooming” them when they were teenagers. One now characterises her alleged encounter with Walliams at 15-years- old as a “sexual assault”.

In a letter to journalists published by the Guardian, Walliams said he was “not a sexual predator” and had not “broken the law”.

He said he “realised that at times I behaved thoughtlessly towards other people I had casual sexual relationships with” and said he regretted not always taking “people’s feelings properly into account”.

Walliams shot to fame alongside Matt Lucas in the early 2000s with BBC sketch comedy Little Britain, and also served as a judge on ITV’s Britain’s Got Talent and launched a best-selling series of children’s books.

The Guardian and ITV News say that several of the women, who do not know one another, allege they were targets of unwanted sexual advances from Walliams.

The allegations include:

In a letter addressed to journalists working on the ITV and Guardian investigation, Walliams wrote: “Looking back, I realise that at times I behaved thoughtlessly towards other people I had casual sexual relationships with.

“I realise I did not always take people’s feelings properly into account. That is something I regret. And whilst a power imbalance is inevitable when one party is famous, abusing that power is something else entirely and it is something that I never did.”

He added: “I am not a sexual predator. I have not broken the law, but I am devastated that some of the women I met 10 to 20 years ago have now expressed hurt or anger towards me.”

After the investigation was published on Tuesday, Walliams’s long-time literary agent Independent Talent Group confirmed it had dropped him.

A BBC spokesperson described the allegations as “serious” and the corporation has removed Little Britain from BBC iPlayer.

Sky also described the allegations as “extremely serious”, saying it was dropping its upcoming adaptation of Walliams’s fantasy feature Fing! and had “already removed content which features him from our platforms”.

The Metropolitan Police said it has contacted the Guardian and ITV News to “to ensure that any potential victims” are “made aware of how they could report any criminal allegations to police”.

One of the women who alleged Walliams “groomed” her as a teenager told BBC Newsnight she was “angry” at his behaviour.

Lilly Creightmore – who Walliams contacted when she was 18 – waived her right to anonymity.

Creightmore told Newsnight that a month after they first met, Walliams told her she “could move in with him and basically that I could be his flatmate”.

She said that after she arrived to stay at his house she “felt instantly pressured to share a bed with him”.

“In the evenings, he would sort of come and sit with me and stroke my leg, and one night I think he put his head in my lap and sort of be like, ‘are you sure you don’t want to come and sleep in my bed with me?’ I had an inner strength like, ‘no I’m not attracted to you in that way’… I felt I was being manipulated,” she added.

She told Newsnight: “I am angry, I’m suppressing it well, but just that this culture of older men in positions of power needs to go, needs to stop. They’re abusing their positions, using young people and abusing young people, and people of any age of course. There were too many men in power still, that are doing this and they need to go.”

Walliams’s lawyers told the ITV News and Guardian investigation that he denied grooming Creightmore or acting inappropriately. They added he did not “target” her because she was “vulnerable” or “young”.

Walliams said he believed his friendship with Lilly was a “special one” and felt “devastated” by her account. He denied the offers of help or gifts were attempts to groom, manipulate or coerce her into sleeping with him.

Two women, given pseudonyms of Alex and Jade in the investigation, have alleged that they first had contact with Walliams when they were 15 years old.

Alex alleged that she met Walliams in 2004 at a fan event when she was 15. She claimed that she and Walliams stayed in touch over the next two years and they had consensual sex for the first time when she was 17, the report alleged.

Asked how she feels about Walliams now, she told the investigation: “I think I was groomed. 100%.”

Walliams told the publications he believed she was 18 at the time they had sex. The investigation said Alex had joked to Walliams in an email she was “old enough to go drinking”, but was actually 17.

Walliams denied grooming Alex. He said he is “mortified to learn” that their “brief, consensual relationship has caused her sadness”.

Jade also alleged she met Walliams when she was 15, in August 2007, in a Soho cafe.

Later, at his home, she alleged, he kissed her, lifted up her T-shirt, went on to commit an act that she now characterises as a sexual assault, and tried to put her hand down his trousers. She referred to what happened that night as “unwanted physical touching and emotional manipulation”.

She said she considers what she says happened to her to have been “grooming”, adding: “It’s completely wrong in every way.”

Walliams strongly denied that he had any sexual contact with Jade. He said he rejected any allegations of criminal activity and says he has never engaged in the grooming of young women.

Another woman, named as Ella, says she was 19 and working as a model when she rejected Walliams when he tried to kiss her during a tour of his home.

She referred to what happened that night as “unwanted physical touching and emotional manipulation”.

Walliams said he made a “clumsy pass” at Ella, and he made no further approaches. He said he had no intention of intimidating Ella, or making her feel uncomfortable.

Other women claimed they were invited to Walliams’s dressing room at Britain’s Got Talent, or contacted by him after attending a taping.

Syco Entertainment, the company that created Britain’s Got Talent, said it had had “no knowledge of the allegations described and was not made aware of them at the time”.

The show’s production company, Fremantle UK, said “no complaint has ever been made” against Walliams and encouraged anyone who “feels they have been the subject of any impropriety or wrongdoing by anyone… to come forward”.

Women who worked for publisher HarperCollins also allege Walliams behaved inappropriately towards younger female employees.

One intern at the company told colleagues she had had a consensual sexual relationship with Walliams, but felt it was an “abuse of power”.

After conducting an internal investigation, HarperCollins announced it was dropping Walliams as an author. Earlier this year, it also said it would no longer be publishing his back catalogue.

In a statement responding to ITV News and the Guardian’s investigation, the company said it takes employee wellbeing “extremely seriously”.

Walliams denies that he sexually harassed anyone at HarperCollins or behaved inappropriately in the workplace.

Walliams, 55, previously brought legal action against Independent Television News (ITN), which makes ITV News, and Guardian News and Media (GNM), publisher of the Guardian, to try and prevent the claims being published.

The two news organisations had argued that they believed it was in the public interest to publish the allegations.

Walliams denied the claims and his lawyers said any publication would be “highly likely” to lead him to kill himself, after two previous suicide attempts, and that the court should prevent any publication or broadcast.

Last week, a High Court judge rejected the injunction request and Walliams did not lodge an appeal, clearing the way for him to be named.