A former senior Facebook executive has told the BBC how the social media giant worked “hand in glove” with the Chinese government on potential ways of allowing Beijing to censor and control content in China.

Sarah Wynn-Williams – a former global public policy director – says in return for gaining access to the Chinese market of hundreds of millions of users, Facebook’s founder, Mark Zuckerberg, considered agreeing to hiding posts that were going viral, until they could be checked by the Chinese authorities.

Ms Williams – who makes the claims in a new book – has also filed a whistleblower complaint with the US markets regulator, the Securities and Exchange Commission (SEC), alleging Meta misled investors. The BBC has reviewed the complaint.

Facebook’s parent company Meta, says Ms Wynn-Williams had her employment terminated in 2017 “for poor performance”.

It is “no secret we were once interested” in operating services in China, it adds. “We ultimately opted not to go through with the ideas we’d explored.”

Meta referred us to Mark Zuckerberg’s comments from 2019, when he said: “We could never come to agreement on what it would take for us to operate there, and they [China] never let us in.”

Facebook also used algorithms to spot when young teenagers were feeling vulnerable as part of research aimed at advertisers, Ms Wynn-Williams alleges.

A former New Zealand diplomat, she joined Facebook in 2011, and says she watched the company grow from “a front row seat”.

Now she wants to show some of the “decision-making and moral compromises” that she says went on when she was there. It is a critical moment, she adds, as “many of the people I worked with… are going to be central” to the introduction of AI.

In her memoir, Careless People, Ms Wynn-Williams paints a picture of what she alleges working on Facebook’s senior team was like.

Mr Zuckerberg, she says, did not get up before midday, loved karaoke and did not like to be beaten at board games, such as Risk. “I didn’t realise that you were supposed to let him win. I was a little naive,” she told us.

However, Ms Wynn-Williams says her allegations about the company’s close relationship with China provide an insight into Facebook’s decision-making at the time.

“China is Mark Zuckerberg’s white whale,” meaning a goal that he obsessively pursued, says Ms Wynn-Williams.

The country is the world’s biggest social media market, but access to Facebook remains blocked there, alongside the likes of X and YouTube.

“It’s the one piece on the board game that he hasn’t conquered,” she says.

Ms Wynn-Williams claims that in the mid-2010s, as part of its negotiations with the Chinese government, Facebook considered allowing it future access to Chinese citizens’ user data.

“He was working hand in glove with the Chinese Communist Party, building a censorship tool… basically working to develop sort of the antithesis of many of the principles that underpin Facebook,” she told the BBC.

Ms Wynn-Williams says governments frequently asked for explanations of how aspects of Facebook’s software worked, but were told it was proprietary information.

“But when it came to the Chinese, the curtain was pulled back,” she says.

“Engineers were brought out. They were walked through every aspect, and Facebook was making sure these Chinese officials were upskilled enough that they could not only learn about these products, but then test Facebook on the censorship version of these products that they were building.”

Meta told the BBC that such claims about China had been “widely reported” at the time.

In her SEC complaint, Ms Wynn-Williams also alleges Mr Zuckerberg and other Meta executives had made “misleading statements… in response to Congressional inquiries” about China.

One answer given by Mr Zuckerberg to Congress in 2018 said Facebook was “not in a position to know exactly how the [Chinese] government would seek to apply its laws and regulations on content”

Meta told the BBC that Mr Zuckerberg gave accurate testimony, adding it did not operate services in China.

Most Facebook executives didn’t allow their own children on Facebook – according to Ms Wynn-Williams. “They had screen bans. They certainly wouldn’t allow them to use the product.”

And yet she says reports from 2017 – that the company had been using algorithms to target and categorise vulnerable teens – were true.

“The algorithm could infer that they were feeling worthless or unhappy,” she alleges.

The company – which also owns Instagram and WhatsApp – could, she claims, identify when a teenage girl had deleted a selfie on its platforms, and then notify a beauty company that it would be a good moment to target the child with an advert.

Ms Wynn-Williams says she “felt sick” at the thought and tried to push back, “although I knew it was futile”.

“They said: ‘The business side thinks this is exactly what we should be doing. We’ve got this amazing product, we can get young people, which is a really important advertising segment.'”

Meta told the BBC this was false – it has never offered tools to target people based on their emotional state – and that the research it previously did was to help marketers understand how people express themselves on Facebook, not to target ads.

Overall, Ms Wynn-Williams says the company has not done enough to address the issue of young people’s safety on social media.

“This is one of the most valuable companies in the world. They could invest in this and make it a real priority and do more to fix it.”

Facebook said it was transparent about advert-targeting and had shared updates regarding its approach to creating age-appropriate advert experiences for teens.

It also said it had introduced “Teen Accounts” for tens of millions of young people with built-in protections. It also said it was giving parents more oversight over their teens’ use of the app.

As well as poor performance, Meta says the 45-year-old was also fired for “toxic behaviour” after she had made “misleading and unfounded allegations of harassment”.

But Ms Wynn-Williams told the BBC she was let go after she had complained about inappropriate comments by one of her bosses – Joel Kaplan, who is now Meta’s chief global affairs officer.

Meta told us she had been paid by “anti-Facebook activists” and she was not a whistleblower.

“Whistleblower status protects communications to the government, not disgruntled activists trying to sell books,” it said.

In regard to Ms Wynn-Williams’ book, Meta has confirmed to the BBC that it has launched legal action in the US to “halt the further distribution of defamatory and untrue information”.

To counter this, a legal representative for Ms Wynn-Williams said: “Meta has made a number of false and inconsistent statements about Sarah since the news of her memoir broke… while Meta’s statements are trying to mislead the public, the book speaks for itself”

We asked her why she was speaking out now. She said she wanted Meta to change as it “influences so much of our day-to-day life” and we need to ensure “we get the future we deserve”.

“We’re in this moment where tech and political leaders are coming together and as they combine forces, that has a lot of consequences for all of us.

“I think it’s really important to understand that and to understand you look at all these engineers who are influencing the highest level of government.”