The personal Twitter account of the Georgia Republican congresswoman Marjorie Taylor Greene has been permanently suspended, for violating policies on Covid misinformation.

The action against Greene on Sunday came under the “strike” system Twitter launched last March, which uses artificial intelligence to identify posts about the coronavirus misleading enough to cause harm.

Two or three strikes earn a 12-hour account lock, four strikes prompt a weeklong suspension and five or more can get an account permanently removed.

Twitter had previously suspended Greene’s account for periods ranging from 12 hours to a week. She was issued a “fourth strike” this summer, for saying vaccines were failing.

“We’ve been clear that … we will permanently suspend accounts for repeated violations of the policy,” a Twitter spokeswoman said on Sunday.

The congresswoman’s official account remains active.

The Republican is a determined controversialist and extremist who courts controversy and confrontation.

On social media, she has voiced support for racist views, QAnon conspiracy theories such as the lie that the 2020 election was stolen, and calls for violence against Democrats including the House speaker, Nancy Pelosi.

Last February, the Republican leader in the Senate, Mitch McConnell, called Greene’s embrace of conspiracy theories and “loony lies” a “cancer for the Republican party”. The Democratic-led House ejected her from committee assignments.

In July, Twitter suspended Greene for a week after Joe Biden urged tech companies to take stronger action against bogus vaccine claims that the president said were “killing people”. Twitter has said it has removed thousands of tweets and challenged millions of accounts.

Greene has regularly been fined for refusing to follow Covid guidelines in Congress, including regarding mask-wearing on the House floor.

In a statement on the Telegram app on Sunday, she called Twitter “an enemy to America” and said it could not “handle the truth”.

She also accused Twitter of seeking “a communist revolution” and said: “Social media platforms can’t stop the truth from being spread far and wide. Big tech can’t stop the truth. Communist Democrats can’t stop the truth. I stand with the truth and the people. We will overcome.”

Greene said her account was suspended after tweeting statistics from the Vaccine Adverse Event Reporting System, a government database which includes raw data.

Among Greene’s final tweets was one that falsely referenced “extremely high amounts of Covid vaccine deaths”, according to her Telegram account, which appears to mirror her now-banned Twitter feed.

More than 825,000 people have died of Covid-19 in the US, out of a caseload of nearly 55m. Many states are experiencing a surge of cases and disruption to everyday life caused by the highly infectious Omicron variant.

On Sunday, Biden’s top medical adviser, Dr Anthony Fauci, said the US had been seeing almost a “vertical increase” of cases, now averaging 400,000 a day with hospitalisations up too.

Resistance to vaccinations and other public health measures has fueled the pandemic and political tensions. Last week, Greene boasted on Twitter about talking to Donald Trump by phone. She said she had received the former president’s permission to clarify his stance that he is against vaccine mandates though he encourages people to get the shot and booster.

Trump was booed by some audience members in Dallas on 19 December, when he said he had received a booster shot.