China cannot accept the World Health Organisation's plan for the second phase of a study into the origins of Covid-19, a senior Chinese health official said today.

Zeng Yixin, China's vice minister of the National Health Commission, said he was shocked by the plan and specifically, the theory that the virus might have leaked from a Chinese lab.

He dismissed the theory as a rumour that runs counter to common sense and science.

"It is impossible for us to accept such an origin-tracing plan," he said in a news conference called to address the Covid-19 origins issue.

The search for the origins of the virus has become a diplomatic issue that has worsened China's relations with the US and many of its allies. The US and others say that China has not been transparent about what happened in the early days of the pandemic. China accuses critics of politicising an issue that should be left to scientists.

Tedros Adhanom Ghebreyesus, the director-general of WHO, acknowledged last week that it was premature to rule out a potential link between the pandemic and a leak from a Chinese government lab in Wuhan, the city where the disease was first detected in late 2019.

Zeng said the Wuhan lab has no virus that can directly infect humans. He noted that a WHO-co-ordinated team of international experts who visited the lab earlier this year concluded that a lab leak was highly unlikely.

Most experts believe the virus most likely jumped from animals to humans. The highly politicised debate centres on whether a lab leak is so unlikely that the theory should be ruled out as a possibility, or if it merits further study.