Facebook, Twitter and Google have been urged by a US lawmaker to ban a dozen people who it is claimed are spreading the vast majority of disinformation about Covid vaccinations.

Representative Mike Doyle made the call to remove their accounts during a US congressional session on how the three firms were dealing with fake news.

He challenged Mark Zuckerberg, Jack Dorsey and Sundar Pinchai to deplatform the dozen people immediately.

None have responded to the call so far.

Facebook said that it was looking into the matter to see if the accounts violated its community standards.

Twitter and Google have not responded to the BBC on the specific request to remove the accounts.

The Center for Countering Digital Hate (CCDH) analysed more than 812,000 Facebook and Twitter vaccine-related posts and found that 65% of anti-vaccine posts came from what it called the "disinformation dozen".

"Anti-vaccine activists on Facebook, YouTube, Instagram and Twitter reach more than 59 million followers, making these the largest and most important social media platforms for anti-vaxxers," the report said.

Three of the 12 have been removed from at least one platform but none have been removed from all. Among the dozen are Robert F Kennedy Jr, a nephew of the former US president who leads an anti-vaccine group; Dr Joseph Mercola; and Ty and Charlene Bollinger.