The appointment makes Clegg, former leader of Britain's Liberal Democrats and deputy to former PM David Cameron between 2010 and 2015, the most senior European politician ever in a leadership role in Silicon Valley.

Facebook said Chief Executive Officer Mark Zuckerberg and Chief Operating Officer Sheryl Sandberg were closely involved in the hiring process, and started talking to Clegg over the summer.

"Our company is on a critical journey. The challenges we face are serious and clear and now more than ever we need new perspectives to help us though this time of change," Sandberg said on a Facebook post congratulating Clegg.

Clegg, 51, succeeds Elliot Schrage and will report to Sandberg starting on Monday.

Clegg was ousted as deputy prime minister after the Conservatives won a majority in 2015 in an election that saw his party suffer a significant loss of support.

Clegg lost his own seat in Britain's parliament in a general election last year.

"Throughout my public life I have relished grappling with difficult and controversial issues and seeking to communicate them to others. I hope to use some of those skills in my new role," Clegg said in a Facebook post.

Schrage, who led the social network's response to its several scandals, stepped down from the role in June after a decade with the company. Schrage will stay as an adviser, Facebook said.

Facebook has faced a barrage of criticism from users and lawmakers after it said last year that Russian agents used its platform to spread disinformation before and after the 2016 US presidential election, an accusation Moscow denies.

In March, the company faced new scrutiny over how it protects personal information after acknowledging that the data of up to 87 million people ended up in the hands of political consultancy Cambridge Analytica.

Australian Associated Press