Britain could suffer 40,000 deaths in first coronavirus outbreak and may be hit by up to ten waves of the infection before the population achieves herd immunity, former World Health Organisation official warns MPs.
Professor Anthony Costello, of University College London's Institute for Global Health, told a committee of MPs that the "harsh reality" is that "we were too slow with a number of things".
"If we're going to suppress the chain of transmission of this virus in the next stage we all hope that the national lockdown and social distancing will bring about a large suppression of the epidemic so far - but we're going to face further waves," he said.
"And so we need to make sure that we have a system in place that cannot just do a certain number of tests in the laboratory, but has a system at district and community level."
Prof Costello, giving evidence to the Commons Health and Social Care Committee, said we "should not have any blame at this stage" but that "we can make sure in the second wave we're not too slow".
Health Secretary Matt Hancock announced that testing will be expanded to those in the police, fire service and prisons, as well as critical local authority workers, the judiciary and Department for Work and Pensions staff where required.
It follows criticism of a gulf between those being tested and the testing capacity, with just 16,000 tests being conducted in the 24 hours up to 9am on Wednesday, despite 35,000 tests being available.
Mr Hancock confirmed to the committee that more than 50,000 NHS workers have now been tested for coronavirus.
MPs were also told that healthcare staff are "genuinely concerned" about the safety of patients being compromised if workers are spread too thinly.
Dr Alison Pittard, Dean at the Faculty of Intensive Care Medicine, said: "We've had to spread ourselves more thinly and we have developed guidance to try and make sure that continues to be safe, but if we have to expand even more and spread ourselves even more thinly, there would be concern that safety could be compromised.
"So everyone is working really well, we're doing everything that we can but staff are genuinely concerned."
And Dame Donna Kinnair, chief executive of the Royal College of Nursing, told the committee sick NHS workers are being forced to drive two hours away to be tested.
She urged: "We need some really clear direction on how we can access testing both in the NHS but more so for social care, because they don't have the same infrastructure as the NHS."