Mr David Icke has promoted fringe theories since the 1990s, but his recent return to prominence was propelled by the spread of Covid-19. “The account referenced has been permanently suspended for violating Twitter’s rules regarding Covid misinformation,” a spokesman told the BBC.
The action comes six months after Facebook and YouTube took similar action, saying Mr Icke had posted misleading claims about the pandemic.
The 68-year-old had about 382,000 followers on Twitter.
His recent posts had included attacks on Prime Minister Boris Johnson, US infectious disease expert Dr Anthony Fauci and the philanthropist Bill Gates.
In a blog, Mr Icke said was banned for a tweet he had made about plans to pilot city-wide coronavirus testing in Liverpool.
But over recent months he has made false claims such as suggesting that 5G mobile phone networks were linked to the spread of the virus, and that a Jewish group had also been involved.
Some campaigners believe action against Mr Icke was long overdue.
“Twitter had allowed him to continue spreading… dangerous Covid misinformation for months,” tweeted the Center for Countering Digital Hate, a UK-based campaign group, in response to the ban.
The US social network had earlier blocked another prominent British conspiracy theorist, Kate Shemirani.
Her account was taken offline on Thursday, with Twitter providing the same brief explanation for its removal.