One of Facebook's earliest investors has labelled the social media giant's plans for a metaverse as "dystopian".
Meta, as Facebook is now known, is investing billions in the project.
But Roger McNamee told the BBC: "It's a bad idea and the fact we are all sitting and looking at this like it's normal should be alarming everyone."
Meta's chief product officer Chris Cox told attendees at the Web Summit in Lisbon that the idea would make "the internet less flat".
He said it would be considerably better than video conferencing as a space for meetings.
However, speaking at the same event, Mr McNamee was highly sceptical.
"Facebook should not be allowed to create a dystopian metaverse," he said.
The term metaverse was coined in the 1990s in a science fiction novel Snow Crash, where it served as a virtual reality successor to the internet.
Mr McNamee became a critic of Facebook as he began to see more misinformation on the platform. He said he was not convinced the metaverse would be safe in chief executive Mark Zuckerberg's hands.
"There's no way that a regulator or policymaker should be allowing Facebook to operate there [in the metaverse] or get into cryptocurrencies," he said.
"Facebook should have lost the right to make its own choices. A regulator should be there giving pre-approval for everything they do. The amount of harm they've done is incalculable."
Mr Cox, speaking for Meta, put forward a different view - that the metaverse idea is the next step for the internet as a whole, not just for his company.
"Technology often starts in lower resolutions versions of what it becomes," he said.
Feedback from Meta's Oculus virtual reality headset users was that the technology, which was improving all the time, could be "incredibly fun".
Mr Cox told Nicholas Carlson, editor-in-chief of news publication Insider, that his own dabbling in the metaverse included hosting meetings and entertainment for staff.
He said he and his wife had watched a comedy show with Facebook employees in which everyone appeared as avatars: "Twenty of us in the room, co-workers, all laughing together."
That same technology was a good alternative to video calls, he argued.
"Everyone is exhausted by video conferencing. You don't know who is looking at who, everyone is constantly interrupting each other."
Meetings in the metaverse would be far better, he said, with Meta working on how to improve "spatial audio and body language" in virtual reality.
When asked why anyone would want to meet in virtual reality, he said: "It will not replace real life - nothing should - and I don't want to design something that does."
He acknowledged that no one company, such as Meta, would own the metaverse, pointing to Roblox as an example.
Roblox, a user-generated gaming platform valued at $30bn (£22bn) and with 43 million users around the globe, has its own plans for the metaverse.
Chief executive David Baszucki has for several years been outlining his vision of it as a digital place where people play, work or learn with millions of 3D experiences.
At Web Summit, Roblox's head of music Jon Vlassopulos told the BBC: "I think our view of the metaverse is that we've been at it for about 15 years.
"So we're ushering in the metaverse, and we feel it needs to be a place that everyone can access, a place where people can express themselves and connect together.
"We've been building around this vision for a long time. We're excited that more people are coming it to validate that notion."
Mr Cox was asked whether the metaverse - which Mr Carlson described as a "cartoon world" - was something that the tech giant should control.
He said that there would need to be "a set of standards and a set of protocols" along with "public discourse" about how to keep the space safe.
He added that Mr Zuckerberg was committed to safety, something he said the "company had been working on for over a decade".