China has angrily rejected White House calls for an investigation into the possibility that Covid-19 escaped from a Wuhan laboratory, a theory that state media described as “a conspiracy created by US intelligence agencies”.

The Biden administration has in recent days begun to push for a fuller investigation into the origins of the pandemic, following a report from the Wall Street Journal. The article said that three employees of the Wuhan Institute of Virology had fallen sick with Covid-19-like symptoms in November 2019, citing an undisclosed US intelligence report.

The Wuhan institute, China’s highest-level biosafety lab, has been at the centre of theories arguing that Sars-Cov-2 may have accidentally infected humans during experiments on bat coronaviruses conducted there.

China has denied that a lab leak was a possible cause and has once again suggested that the virus was just as likely to have come from US biolabs.

Chinese state media also took aim at Anthony Fauci, the leading US infectious disease expert, who recently voiced support for further investigation, saying that he was not “100 per cent” sure that the outbreak had natural origins.

Fauci was “fanning a huge lie against China”, wrote Hu Xijin, editor of the Global Times, a nationalist tabloid published by the Communist party’s official People’s Daily newspaper.

The theory of a lab accident is “a conspiracy created by US intelligence agencies and the media outlet to slander China”, he added. “Is it a coincidence that Fauci repeated such lines?”

Andy Slavitt, one of the Joe Biden coronavirus advisers, on Tuesday said the World Health Organization investigation, carried out jointly with Chinese scientists this year, had not done enough to explain how the disease first started spreading among humans.

“We need to get to the bottom of this and we need a completely transparent process from China,” he said.

The WHO report released in March concluded that the lab leak hypothesis was “extremely unlikely”, but it has been criticised for being too credulous of analysis presented by Chinese scientists and for failing to provide enough evidence to rule out a leak.

Tedros Adhanom Ghebreyesus, the WHO director-general, subsequently admitted that further investigation was needed to draw firm conclusions about the origins of the virus, which has killed almost 3.5m people.

Researchers at the Wuhan Institute of Virology last week released a research paper arguing that the virus strains found in bats in south-west China were “just the tip of the iceberg” for potential ancestors of Sars-Cov-2. They added that the strains were unlikely to be ancestors for the virus without first infecting an intermediate animal host.

Shi Zhengli, WIV’s leading expert on coronaviruses and whose work on bat coronavirus has been the focal point of the lab theories, was one of the authors.

The bat viruses studied in the paper, which has not been peer reviewed, lacked the ability to bind with proteins known as human ACE2 receptors, which are an important part of Sars-Cov-2’s ability to infect people, and thus “pose little spillover potential to human without future adaptation”, the authors wrote.