Around 136,000 people in England currently have the coronavirus, according to scientists.
The figure - based on research by the University of Oxford and the Office of National Statistics - is much higher than previous estimates based on testing.
It means 0.24 per cent of adults - or one in every 400 - are infected with the deadly bug and some could be spreading it unwittingly.
Carl Heneghan, a professor of epidemiology at the University of Oxford, says the data suggests the peak of the UK's coronavirus outbreak in April was much worse than previously thought.
"To me it suggests that, at peak, we had loads more cases than we realised," he told the Sun.
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"It shows we have nearly 140,000 infected with Covid, which is far more than we are picking up through testing.
"Fewer than 4,000 people a day are testing positive. Why are the rest of these cases not coming forward. Is it because they are asymptomatic?"
The study, carried out by the University's Centre for Evidence-Based Medicine, is the first which tries to gauge what proportion of the UK public is currently ill with Covid-19.
It suggests that the virus is not at epidemic levels, which would require the surveillance rate to be higher than 40 per 10,000.
The data - based on swabs from 7,087 people taken between April 26 and May 8 - suggests this figure is between 24 and three in 10,000.
It comes as the UK's coronavirus death toll rose to more than 32,000 yesterday following a further 210 deaths in hospitals, care homes and the wider community.
However, the daily rise is the lowest rise since March 26, when 183 people were recorded as dying of Covid-19.
As of 9am May 11, there have been 1,921,770 tests, with 100,490 tests on 10 May, said the Department of Health.
1,400,107 people have been tested of which 223,060 tested positive.
As the UK death toll continued to tick upwards Prime Minister Boris Johnson addressed the nation on Sunday night in a special televised address.
He announced that the road out of the coronavirus lockdown would be a long one, before suggesting that people who could not work from home were now advised to go back into work if they could do so safely.
Speaking in the House of Commons yesterday afternoon, he also praised "the indomitable spirit of Britain."
The Prime Minister urged people to continue following the rules to keep new infections down, and gain control of the spread of the coronavirus.
