Whistleblower Frances Haugen issued a stinging rebuke of Facebook's "Meta" rebrand on Monday, accusing the company of yet again prioritising expansion over people's safety.
The former Facebook engineer, who leaked a trove of internal documents that have sparked weeks of criticism of the social media giant, also called on its chairman and CEO Mark Zuckerberg to step down.
Speaking at the Web Summit tech conference in Lisbon, Haugen said it was "unconscionable" that Facebook was trumpeting its ambitions to develop the "metaverse" -- a virtual reality version of the internet -- rather than focusing on fixing existing problems.
"Over and over again Facebook chooses expansion in new areas over sticking the landing on what they've already done," she told an audience of tens of thousands in the Portuguese capital.
"Instead of investing in making sure their platforms are a minimum level of safe, they're about to invest 10,000 engineers in video games."
Facebook last month announced that it will hire 10,000 new staff in Europe over the next five years in its bid to build the metaverse, which would use virtual reality to make online experiences -- like chatting to a friend, or attending a concert -- feel face-to-face.
The company last week announced it was changing the name of Facebook's parent company to "Meta" to signal the change in focus.
Critics have derided the rebrand as an attempted distraction from the avalanche of damaging revelations from Haugen's leaked documents.
The "Facebook Papers" show that company executives knew of their sites' potential for harm on numerous fronts, including the uncontrolled spread of hate speech in developing countries as well as Instagram's impact on teens' mental health.
Haugen has accused Facebook of ignoring concerns raised by its own employees in the pursuit of profit.
- 'Overwhelming' -
Asked if Zuckerberg should step down, she said: "I think Facebook would be stronger with someone who's willing to focus on safety, so yes."
She went on: "It doesn't make him a bad person to have made mistakes, but it is unacceptable to continue to make the same bad mistakes after you know that those are mistakes."
Haugen has testified before US and UK lawmakers in recent weeks, but the Web Summit -- which she officially opened, with an explosion of confetti raining down from the ceiling -- marked her first appearance before a wider public.
She said it was "overwhelming" to speak in front of so many people, telling the crowd: "Right now my heart is beating about as fast as I can imagine."
Facebook vice president Nick Clegg, who is due to address the Web Summit on Tuesday, will likely reject Haugen's suggestion that the metaverse project equates to a mass investment in "video games".
Zuckerberg last week showcased a much-mocked promo of what the metaverse could eventually look and feel like -- which was indeed playful, involving flying koi carp and a card game with a robot.
But Silicon Valley enthusiasts believe the metaverse could represent the next great leap in the evolution of the internet, eventually blurring the digital world seamlessly with the physical one, creating a wealth of new economic opportunities.
The metaverse is the theme of numerous events at this year's Web Summit, which runs through Thursday.
"I think some of the discussion will be, 'how much of it is hype and how much of it is real?'" Web Summit CEO Paddy Cosgrave told AFP.
Some 40,000 attendees are flying into Portugal for the tech conference -- all of them requiring proof of vaccination or a negative PCR -- in a test of the return to mass events.
Organizers have hailed the fact that host country Portugal enjoys one of the world's highest vaccination rates.