OpenAI plans to allow a wider range of content, including erotica, on its popular chatbot ChatGPT as part of its push to "treat adult users like adults", says its boss Sam Altman.

In a post on X on Tuesday, Mr Altman said upcoming versions of the popular chatbot would enable it to behave in a more human-like way - "but only if you want it, not because we are usage maxxing".

The move, reminiscent of Elon Musk's xAI recent introduction of two sexually explicit chatbots to Grok, could help OpenAI attract more paying subscribers.

It is also likely to intensify pressure on lawmakers to introduce tighter restrictions on chatbot companions.

OpenAI did not respond to the BBC's requests for comment following Mr Altman's post.

Changes announced by the company come after it was sued earlier this year by parents of a US teen who took his own life.

The lawsuit filed by Matt and Maria Raine, who are the parents of 16-year-old Adam Raine, was the first legal action accusing OpenAI of wrongful death.

The Californian couple criticised the company's parental controls - which it said were designed to promote healthier use of its chatbot - saying they did not go far enough.

The family included chat logs between Adam, who died in April, and ChatGPT that show him explaining he has suicidal thoughts.

Altman said that OpenAI previously made ChatGPT "pretty restrictive to make sure we were being careful with mental health issues".

"We realise this made it less useful/enjoyable to many users who had no mental health problems, but given the seriousness of the issue we wanted to get this right," Mr Altman said.

He said the company has now been able to mitigate the serious mental health risks and have new tools allowing it to "safely relax the restrictions in most cases".

"In December, as we roll out age-gating more fully and as part of our 'treat adult users like adults' principle, we will allow even more, like erotica for verified adults," he said.

Critics say OpenAI's decision to allow erotica on the platform shows the need for more regulation at the federal and state levels.

"How are they going to make sure that children are not able to access the portions of ChatGPT that are adult-only and provide erotica?" said Jenny Kim, a partner at the law firm Boies Schiller Flexner. "Open AI, like most of big tech in this space, is just using people like guinea pigs."

Ms Kim is involved in a lawsuit against Meta that claims the company's Instagram's algorithm harms the mental health of teen users.

"We don't even know if their age gating is going to work," she said.

In April, TechCrunch reported that OpenAI was allowing accounts in which a user had registered as a minor to generate graphic erotica.

OpenAI said at the time that the company was rolling out a fix to limit such content.

A survey published this month by the nonprofit Centre for Democracy and Technology (CDT) found that one in five students report that they or someone they know has had a romantic relationship with AI.

On Monday, California Governor Gavin Newsom vetoed a bill passed by the state legislature that would have blocked developers from offering AI chatbots companions to children unless the companies could guarantee the software wouldn't breed harmful behaviour.

Newsom said it was "imperative that adolescents learn how to safely interact with AI systems" in a message that accompanied his veto.

At the nationwide level, the US Federal Trade Commission (FTC) has launched an inquiry into how AI chatbots interact with children.

In the US Senate last month, bipartisan legislation was introduced that would classify AI chatbots as products. The law would allow users to file liability claims against chatbot developers.

Mr Altman's announcement on Tuesday comes as sceptics have been questioning the rapid rise in the value of AI tech companies.

OpenAI's revenue is growing, but it has never been profitable.

Tulane University business professor Rob Lalka, who authored the recent book The Venture Alchemists, said the major AI companies find themselves in a battle for market share.

"No company has ever had the kind of adoption that OpenAI saw with ChatGPT," Lalka told the BBC.

"They needed to continue to push along that exponential growth curve, achieving market domination as much as they can."