A scientist who advises the government on coronavirus says he wishes the UK had gone into lockdown sooner as the delay had “cost a lot of lives”.
But Prof John Edmunds said data available in March was “really quite poor”, making it “very hard” to do so.
Health Secretary Matt Hancock says the government “took the right decisions at the right time”.
The comments come as the prime minister is set to announce more easing of lockdown measures for 15 June.
Boris Johnson is expected to tell cabinet about the additional changes on Tuesday.
It has also been revealed the PM plans to give a speech in the summer, setting out his vision for how the UK can recover from the coronavirus crisis.
He is expected to return to his promise to “level up” the country and reach out to new Conservative voters who helped him win power in December’s election.
Mr Hancock told the BBC’s Andrew Marr that the government would take a “very cautious and safety first” approach to further relaxation of the rules.
Labour’s shadow foreign secretary, Lisa Nandy, said her party supported easing the lockdown but called for improvements in the government’s test and trace system to ensure it was safe and more help for those in isolation.
Mr Hancock also said the government had reached its target this weekend of delivering tests to all staff and residents of care homes.
But Labour’s shadow minister for social care, Liz Kendall, said the original pledge had been for tests to have been carried out, not just delivered to care homes, and accused the government of being “too slow to act”.
Boris Johnson announced the lockdown on 23 March, with new restrictions added in April.
The lockdown has already begun to be eased, with changes across the UK around the number of people you could meet up with from outside your household coming into force this week, and the reopening of schools for some pupils in England.
Further easing is due from 15 June in England, with non-essential retailers allowed to re-open and places of worship allowed to open for private prayer.
Downing Street said any alterations to lockdown measures in the coming weeks would depend on the government’s five tests continuing to be met, in order to prevent a second spike in the virus and stop the NHS being overwhelmed.
These include ensuring the R number – the number of people an infected person passes the virus onto -stays below one.
Speaking to Andrew Marr, Prof Edmunds warned the R was “creeping up” in some places – with some reports suggesting it had gone above one in north-west England.
But Mr Hancock said the estimated R was “below one in each region”, and the government would “take local action in the first instance to crack down on any local outbreak” – including reintroducing lockdown measures.
The Labour mayors for Greater Manchester and Liverpool, Andy Burnham and Steve Rotherham, said talk of local lockdowns were “not helpful”, and accused the government of “unacceptable” behaviour for not including them in the planning.
They said if the government was “determined to proceed” with the measure, “significant support needs to be put in place” for English regions, including a local furlough scheme and funding for councils.
‘Data was poor’
Looking back, Prof Edmunds said it would have been “very hard to pull the trigger” for lockdown earlier, saying the data they had and the “situation awareness” was “really quite poor”.
But, he added: “I wish we had gone into lockdown earlier. I think that has cost a lot of lives unfortunately.”
Asked about the comments, Mr Hancock said: “I think we took the right decisions at the right time.”
The health secretary said there was a “broad range… of scientific opinion” on the government’s Scientific Advisory Group for Emergencies (Sage) and Prof Edmunds was one among more than 100 members.
“We were guided by the science – which means guided by the balance of that opinion – as expressed to ministers through the chief medical officer and the chief scientific adviser,” he added.
“That’s the right way for it to have been done.”