Britain is still filling less than half its coronavirus testing capacity a week before the deadline to reach 100,000 a day.
Downing Street has admitted there is a "great deal more to do" to fill the gap between capacity and the number of people actually getting tested for Covid-19.
The capacity for tests in England, Scotland and Wales is now 48,273 a day.
Yet just 22,814 coronavirus tests were carried out on 13,522 people in the 24 hours up to 9am on Wednesday.
That means the government faces a struggle to meet its target of carrying out 100,000 tests a day by April 30.
The Prime Minister's official spokesman said: "The number of people we've tested has increased in the most recent 24 hours we've got figures for.
"And the gap between the number of people tested and the number of people we've tested has closed slightly.
"But that doesn't distract from the fact that there's a great deal more to do if we're to be able to say we're making the full use of the capacity we have."
It comes after ministers were accused of moving the goalposts over Health Secretary Matt Hancock's controversial 100,000-a-day target.
Yesterday Dominic Raab, the stand-in PM, tried to suggest critics should look at testing capacity, not the actual number of tests.
But today the PM's spokesman confirmed the target was indeed about the number of tests carried out.
Around 50 drive-through sites will be ready by end of the month with 28 already open, the No10 spokesman said.
"The mobile units will visit the care homes and test any residents and staff and separately we're using Amazon to deliver tests to people's homes," he added.
Earlier today a Cabinet minister admitted it is "dreadful" that care workers are struggling to access coronavirus tests.
Northern Ireland Secretary Brandon Lewis faced intense scrutiny over the Government's struggle to reach its 100,000-a-day target.
With high numbers of deaths expected in care homes, staff have been raising concerns that they cannot access testing to determine whether their symptoms are caused by Covid-19.
Mr Lewis was subjected to fierce criticism by Piers Morgan, who described his talk of testing capacity as "meaningless" when carers cannot access the tests.
"I'm agreeing with you, Piers, I think it's dreadful that we can't get more people tested," Mr Lewis replied on ITV's Good Morning Britain.
Mr Lewis tried to shift the focus on to testing capacity having exceeded 40,000, despite less than half of that being used so far.
But he conceded that the target set by Health Secretary Matt Hancock is for 100,000 tests a day to be carried out by the end of the month.
"The target is still to do 100,000 tests a day," Mr Lewis said.
