McNamee was one of the earliest investors but has hit out at the firm's plans to construct a virtual reality successor to the internet.
Facebook has recently been renamed Meta and the company's chief product officer Chris Cox told the Web Summit in Lisbon that the concept would make "the internet less flat".
McNamee became a critic of Facebook as a result of the misinformation on the site and he doubts that the metaverse will be a success in the hands of Mark Zuckerberg.
He told BBC News: "It's a bad idea and the fact we are all sitting and looking at this like it's normal should be alarming everyone.
"Facebook should not be allowed to create a dystopian metaverse."
McNamee continued: "There's no way that a regulator or policymaker should be allowing Facebook to operate there [in the metaverse] or get into cryptocurrencies.
"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."
However, the metaverse does have support from Roblox's head of music Jon Vlassopulos - who feels that it is the realisation of several years of work.
He 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."