A “collective failure” to appreciate the enormity of the coronavirus pandemic and enact swift measures to protect the public will lead to unnecessary deaths, according to a leading doctor who says the UK ignored clear warning signs from China.

Richard Horton, the editor-in-chief of the Lancet, rounded on politicians and their expert advisers for failing to act when Chinese researchers first warned about a devastating new virus that was killing people in Hubei eight weeks ago.

The team from Wuhan and Beijing reported in January that the number of deaths was rising quickly as the virus spread in China. They urged the global community to launch “careful surveillance” in view of the pathogen’s “pandemic potential”.

But writing in the Guardian, Horton said the warning was met with complacency in Britain, where he said for unknown reasons medical and scientific advisers watched and waited. Initially, scientists advising ministers appeared to believe the coronavirus could be treated like influenza, and that a “controlled epidemic” would generate “herd immunity” that would help protect the most vulnerable against the infection. The scenario called for upwards of 60% of the population to contract the virus.

The government’s strategy changed dramatically on Monday when the prime minister announced that new modelling from Imperial College London demonstrated that more draconian measures were needed to reduce the projected death toll from 260,000 to about 20,000. Without those measures, which have transformed society, the NHS would be overwhelmed, leading to a situation like that which has driven a relatively high death toll in Italy.

Horton said nothing in the science had changed since January. “The UK’s best scientists have known since that first report from China that Covid-19 was a lethal illness. Yet they did too little, too late,” he said.

Horton has been a vocal critic of the government’s approach to the coronavirus pandemic from the start, and his concerns have been echoed by many scientists who work on infectious disease outbreaks.

Devi Sridhar, a professor of global public health at the University of Edinburgh, tweeted: “We had the data. We had time. We should have learned from this data in early Jan and anyone looking at this from a public health/medical side has been worried about the stress on the health system, in every country.”

Horton said he had “utmost respect” for Chris Whitty, the chief medical adviser, and Patrick Vallance, the chief scientific adviser, but he added: “Somewhere there has been a collective failure among politicians and perhaps even government experts to recognise the signals that Chinese and Italian scientists were sending.”

While the UK was now taking the right actions to quell the outbreak, Horton said, in due course “there must be a reckoning” where difficult questions would have to be asked and answered. “We have lost valuable time. There will be deaths that were preventable. The system failed,” he said.