Ministers should have been prepared to act in the “absence of scientific certainty” in the early stages of the outbreak, an Institute for Government report said.
The IfG also criticised the Government’s ambition to reach 100,000 tests per day by the end of April, saying it had not been well thought through.
It said the Government “lacked a wider sense of strategy” at times.
It accused Health Secretary Matt Hancock of making the testing commitment “without a strong enough sense of how the Government would use additional capacity”.
A Government spokesman defended the response to the crisis, saying ministers “make no apology for being guided by the best scientific advice”.
The IfG report said: “Ministers made much of ‘following the science’. But it is not enough to use evidence: ministers and civil servants also need to understand the limitations of both the evidence base and the forums through which it is channelled, and, difficult as it might be, ministers must be prepared to act in the absence of scientific certainty.
“Failure to do so now seems likely to have cost a significant number of additional lives, and contributed to the UK suffering the highest excess death rate in Europe over the period to the end of May.”
The IfG also said that while school closures and social distancing measures were contemplated in February, some “key aspects of making them work – like remote learning arrangements for schools and guidance for police – were not considered until after decisions had been made”.
However, the report praised the successful rollout of economic support measures, which the IfG said showed that ministers and officials “can find fast ways to consult those who will be affected by a policy or programme and think through how it will be carried out, before making a decision”.
A Government spokesman said: “We make no apology for being guided by the best scientific advice during this unprecedented global pandemic – as the public would expect.
“We keep our response under constant review and have been prepared to adapt as new evidence emerges and we learn more about this virus.
“Working closely with the public and private sectors we rapidly built the largest diagnostics infrastructure in British history.”