More than one in 10 people testing positive for coronavirus do not find out for at least two days after doing the test.
A scientist scrutinising daily test data has found that the time it takes to report a test result has soared since August.
The revelation comes amid a testing scandal which is seeing people all over the country unable to book tests or directed to centres hundreds of miles from home.
Professor Alastair Grant, from the University of East Anglia, found that the proportion of results being reported within 48 hours of the swab plummeted from around 70 per cent at the end of August to just nine per cent on September 15.
He put this down to a backlog in the testing system. Health Secretary Matt Hancock has admitted there is a build-up of something less than a full day’s work for the labs.
Capacity is currently running at a claimed 244,000 tests per day, meaning there could be up to a quarter of a million tests waiting to be processed.
The backlog is also making people less able to get tests, and the Government’s own data shows one in 20 people has to travel nearly 50miles to a test site.
Department of Health statistics released today show that 75 per cent of people get access to a test within 13miles of their home, while five per cent have to go 47 miles.
‘Until the end of August, about 70 per cent of tests were reported two days after swabs were taken,’ said Dr Grant. ‘But this has been falling steadily. On Tuesday 15th September, this figure had fallen to nine per cent’
Professor Grant, explaining the delay in test result processing, said: ‘There has been growing concern about problems in getting a Covid test done over the past few days.
‘The problems seem to be a consequence of the laboratories that process the tests reaching capacity.
‘Backlogs of unprocessed samples are building up, and limits are being placed on the number of testing slots made available to try to control this.’
He posted his findings on a blog on the website of the University of East Anglia.
Dr Grant, a marine biologist by training, was previously the associate dean of science at the university.
He worked out the percentage, he said, by comparing local authority cases with the numbers of positive tests in the central Government database.
‘Until the end of August, about 70 per cent of tests were reported two days after swabs were taken,’ said Dr Grant.
‘But this has been falling steadily. On Tuesday 15th September, this figure had fallen to nine per cent… 40 per cent of the tests reported that day were for specimens taken four or more days previously.’