Facebook whistleblower Frances Haugen on Wednesday said she was "extremely concerned" about the company's plans to build a "metaverse" -- a virtual reality version of the internet -- because of privacy problems.

Faced with a barrage of bad publicity due to Haugen's revelations, Facebook CEO Mark Zuckerberg announced plans late last month to create a digital world where people feel as if they are face-to-face using virtual reality technology.

Speaking to the French parliament on Wednesday during a European tour, Haugen said that she was "extremely concerned about the metaverse".

Facebook "wants to fill our environment with sensors, microphones, other kinds of ways of monitoring us" and the adoption of the technology by companies would be "super problematic".

"Let's imagine you work from home and your employer decides 'I want to be a metaverse company'," she told lawmakers.

"You don't get to decide if Facebook can spy on you like you can opt out from using Facebook in your personal life," she added.

The former Facebook engineer leaked a trove of internal documents to the media that have sparked weeks of criticism of the social media giant over its impact on fragile democracies and vulnerable teens.

During her testimony to American and European lawmakers over the last month, she has insisted that Facebook chooses profit over curtailing toxic content and that the company cannot be trusted to change its ways.

Zuckerberg has hit back, saying that "the argument that we deliberately push content that makes people angry for profit is deeply illogical".

Haugen, a 37-year-old data scientist, also told the French parliament about how she had coped with the scrutiny and public exposure since identifying herself in early October as the main source of a series of explosive reports by the Wall Street Journal.

"Providing psychological support is critical for many whistleblowers," she said, adding that she had been lucky to move back to live with her mother last year because of Covid-19 lockdowns.

"My mother is a priest and I received countless hours of counselling and therapy," she said.

"Most whistleblowers don't have that level of support. Making sure that there is someone that can coach them through the process is vitally important."

Facebook reported profits of $9 billion in the July-September quarter of the year.