LONDON — The British government failure to impose a lockdown in the early days of the COVID-19 pandemic ranks among England's worst public health blunders, lawmakers concluded Tuesday in the country's first comprehensive report on the pandemic.

The deadly delay led to thousands of unnecessary deaths and derived from the failure of government ministers to question the recommendations of scientific advisers, resulting in a dangerous level of "groupthink" that caused them to dismiss the more aggressive strategies adopted in East and Southeast Asia, the report said.

It was only when Britain's National Health Service risked being overwhelmed by rapidly rising infections that Prime Minister Boris Johnson's Conservative government finally ordered a lockdown. in late March 2020.

"Decisions on lockdowns and social distancing during the early weeks of the pandemic – and the advice that led to them – rank as one of the most important public health failures the United Kingdom has ever experienced,'' states the joint report from the House of Commons' science and health committees. "Painful though it is, the U.K. must learn what lessons it can of why this happened if we are to ensure it is not repeated.''

Lawmakers said their inquiry was designed to uncover why the U.K. performed "significantly worse" than many other countries during the initial period of the pandemic. The U.K. has recorded more than 137,000 coronavirus deaths, the highest toll in Europe after Russia.

But government officials said they did what they could with the information they had in a time of crisis.

"It was an unprecedented pandemic," Cabinet minister Stephen Barclay told Sky News. "We were learning about it as we went through, and of course with hindsight, there's things we know about it now that we didn't know at the time." 

Bereaved families reacted to the parliamentary report with outrage, furious that the people who died of COVID-19 received scant mention in the 150-page document. They said the joint committee only was interested in "speaking to their colleagues and friends.''

"The report it's produced is laughable and more interested in political arguments about whether you can bring laptops to…meetings than it is in the experiences of those who tragically lost parents, partners or children to COVID-19,'' said Hannah Brady, spokesperson for COVID-19 Bereaved Families for Justice. "This is an attempt to ignore and gaslight bereaved families, who will see it as a slap in the face.''

Lawmakers released their findings amid frustration with the timetable for a formal public inquiry into the government's response to COVID-19. Johnson says the inquiry will start next spring. 

The report was based on testimony from 50 witnesses, including former Health Secretary Matt Hancock and former government insider Dominic Cummings. It was unanimously approved by 22 lawmakers from the three largest parties in Parliament: the governing Conservatives and the opposition Labour Party and the Scottish National Party.

The committees praised the government's early focus on vaccines as the ultimate way out of the pandemic and its decision to invest in vaccine development. These decisions led to Britain's successful inoculation program, which has seen almost 80% of people 12 and over now fully vaccinated.

"Millions of lives will ultimately be saved as a result of the global vaccine effort in which the U.K. has played a leading part," the committees said. 

But they also criticized the government's test-and-trace program, saying its slow, uncertain and often chaotic performance hampered Britain's response to the pandemic.

The government's strategy during the first three months of the crisis reflected official scientific advice that widespread infection was inevitable given that testing capacity was limited; that there was no immediate prospect for a vaccine; and the belief that the public wouldn't accept a lengthy lockdown, the report said. As a result, the government sought merely to manage the spread of the virus, instead of trying to stop it altogether.

The report described this as a "serious early error" that the U.K. shared with many countries in Europe and North America.

"There was a groupthink that the way you tackle a pandemic should be similar to a flu pandemic," Jeremy Hunt, a former British health minister who now heads Parliament's health committee, said. "I was part of that groupthink, too, when I was health secretary. "

Hunt said that before the coronavirus hit, "an American university said we were the second-best prepared country in the world" for a pandemic.

"We know that clearly wasn't the case," he said.

Trish Greenhalgh, a professor of primary care health services at the University of Oxford, said the report "hints at a less-than-healthy'' relationship between government and scientific bodies. With COVID-19 still killing hundreds of people every week in Britain, advisory committees continue to debate exactly what evidence is "sufficiently definitive" to be considered certain, she said.

"Uncertainty is a defining feature of crises,'' Greenhalgh said. "Dare we replace 'following the science' with 'deliberating on what best to do when the problem is urgent but certainty eludes us'? This report suggests that unless we wish to continue to repeat the mistakes of the recent past, we must." 

Even senior officials like Cummings and Hancock told the committees they were reluctant to push back against scientific consensus.

Hancock said as early as Jan. 28, 2020, he found it difficult to push for widespread testing of people who didn't show symptoms of COVID-19 because scientific advisers said it wouldn't be useful.

"I was in a situation of not having hard evidence that a global scientific consensus of decades was wrong but having an instinct that it was," he testified. "I bitterly regret that I did not overrule that scientific advice."