The government has missed its target to reach 25,000 coronavirus tests a day as more than half of capacity lies unfilled.
A government statement on March 18 said testing would be ramped up to 25,000 a day "within four weeks" - which came to an end yesterday.
But as of 9am yesterday, 15,994 tests had been carried out in Britain in the previous 24 hours. At no point has the number topped 20,000.
That is despite Downing Street saying today that total daily testing capacity is now over 35,000.
The figures are likely to spark a blame game between the government and health officials.
Health Secretary Matt Hancock last night tried to disown the 25,000 target, suggesting it had been superseded when the government pledged 100,000 tests by the end of this month.
And Downing Street today said the government had been "very clear" that spare tests should be used on NHS and social care staff.
The testing capacity breaks down as 20,771 in the NHS, Public Health England and devolved governments, plus 14,300 through commercial drive-through testing sites, No10 said.
In terms of the number actually carried out, it was 13,950 tests in the first pillar including the NHS and just over 2,040 by commercial partners.
The number of tests rose slightly to 18,665 in the 24 hours to 9am today - but were still well under the target.
No10 said overall 60,000 NHS and social care staff and relatives have now been tested, up 6,000 in a day.
But Downing Street was unable to say how many tests have been given to social care staff - only that 4,000 have been "invited" for tests.
Questioned about why so much capacity is still unfilled, the PM's official spokesman said: "We have been very clear that where there is spare capacity available that should be used on NHS staff and their families and in social care.”
The spokesman added: "The Health Secretary was asked about this... he said we’re building testing capacity all the time and the reason the figures have been flat in recent days have been because of a lack of demand, not a lack of capacity.
"We’ve been through a long Bank Holiday weekend but the capacity is there.
"And I think we are very clear we want the NHS to be making use of any additional capacity which exists."
Critics have blamed the government for being slow to expand eligibility for tests.
Until this week, only five residents in each care home were being tested and care home staff with symptoms could not access tests unless they ended up in hospital.
That rule has now changed - plus people leaving hospital for a care home will now be tested before they are placed in that care home.
No10 insisted: "The eligibility has been expanded in recent days."
The 25,000 a day target was one of many announced by the government.
Ministers insist the main target is now to carry out 100,000 tests a day, despite the fact there are now less than two weeks left to meet it.
Mr Hancock already said the 100,000 would include antibody tests - which show if people have had Covid-19 in the past, not now.
But he later said all 100,000 would be "swab" tests which show if people currently have Covid-19, because no antibody test has yet been approved.
Almost a month after the first possible antibody tests began checks in Oxford, No10 said today: "We have not yet found an antibody test that works effectively.
"We continue to try to make progress on that."
Meanwhile, Downing Street today pleaded for people to stop “speculating” about when the lockdown will be lifted.
The PM’s spokesman it is “really important the message to the public is clear - people need to stay at home, protect the NHS and save lives.”
Asked if refusing to tell the public about lockdown and an exit plan at the same time was “patronising”, the spokesman said: “Flatly reject the premise of that question.
“Different countries are at different stages in the pandemic. Our focus has to be for now on slowing the rate of the transmission and making sure we have passed the peak.”
No10 said another 40 UK-built ventilators will arrive at a military base today for use shortly in the NHS.
The ‘Penlon’ devices have been adapted from existing designs by a consortium of firms, rather than built from scratch.
They come on top of other Penlon ventilators which have been arriving since April 1.
Downing Street said there are now more than 10,000 ventilators in total available to NHS patients.
But No10 said just 2,000 further mechanical ventilatros are on order, sparking confusion.
The government previously said a total of 16,000 ‘off the shelf’ ventilators were either in place or on order.
That number now appears to have fallen to 12,000.
In total, 15,000 ventilators have been ordered from Penlon on top of the 12,00 figure.
Hundreds more of them are to be built over the coming weeks. No10 said: “We are moving towards a position where we will have in excess of 20,000 ventilators”.
But that target has been revised down from 30,000 after lockdown eased the strain on the NHS.
