The extremist Republican Marjorie Taylor Greene “might be a Democrat – or just an idiot” – according to a fellow hardline conservative.

Dan Crenshaw, a Texas congressman and former Navy Seal, threw the barb back at the Georgia congresswoman in a spat over his support for using the Federal Emergency Management Agency (Fema) to operate Covid testing sites.

The US is experiencing a crippling surge of Covid cases thanks to the infectious Omicron variant, with more than 1m recorded on Monday and lack of access to testing hampering state and federal responses.

Greene has consistently spread Covid conspiracy theories. On Sunday, she was permanently suspended from Twitter, for spreading misinformation.

That drew support from Donald Trump, who without discernible irony called Twitter “a disgrace to democracy”, said Greene had “a huge constituency of honest, patriotic, hard-working people”, and added: “Keep fighting, Marjorie!”

Regardless, on Monday Greene was temporarily suspended from Facebook, for spreading misinformation.

She took aim at Crenshaw on Instagram, writing: “No Fema should not set up testing sites to check for Omicron sneezes, coughs and runny noses.

“And we don’t need Fema in hospitals, they should hire back all the unvaccinated [healthcare workers] they fired.

“He needs to stop calling himself conservative, he’s hurting our brand.”

Crenshaw responded on Instagram, saying: “Hey, Marjorie, if suggesting we should follow Trump policy instead of Biden mandates makes you mad, then you might be a Democrat – or just an idiot.”

Greene has been repeatedly fined for failing to wear a mask on the floor of the House of Representatives.

Crenshaw, however, has his own history of provocative behaviour.

As the Houston Chronicle pointed out, “Before calling for federally funded testing sites, Crenshaw used to share wild posts to social media, before Greene took office, including posting action movie-style videos of him beating up Antifa members.”

More than 827,000 people have died in the US from Covid-19.