Just 2,000 frontline NHS staff in England have been tested for the coronavirus, Downing Street has said.
The figure comes as Boris Johnson is under increasing pressure over Covid-19 tests as health care leaders warned there is "no immediate prospect" of mass NHS staff testing.
The UK's current testing capacity is 12,750 a day.
On Monday 30th March 8,630 UK tests were carried out, No 10 has said.
Chris Hopson, the chief executive of NHS Providers, which represents NHS trusts, said maximum testing capacity in the UK was currently "very constrained" at around 13,000 tests per day.
Mr Hopson said one NHS trust can only test three staff members a day due to a lack of swabs.
The 2000 frontline members of staff tested represents less than 1% of the 1.2 million people who work for the NHS in the UK.
But the government and experts have said that while they are committed to upscaling testing of frontline workers aiming to test every member of staff, many of who do not work in frontline care, would not be a priority.
At present, the focus is on testing patients in hospital to see if they have coronavirus, with NHS trusts told earlier in the week they should use up to 15% of any spare testing capacity for NHS staff.
Health Secretary Matt Hancock has now scrapped that cap, telling NHS hospital labs to use all spare capacity to test their frontline workers.
Housing and Communities Secretary Robert Jenrick said the government was aiming to "build on NHS staff testing significntly".
He told Radio 4's Today programme: "Clearly that's a low number but one we want to build on significantly.
"We now have capacity today to be testing 12,750 people and we expect that within a couple of days to be 15,000.
"So we should now have the growing capacity to test NHS staff in addition to the patients in critical care."
Mr Jenrick denied the Government and Public Health England (PHE) would only agree to centralised testing after claims from scientists and universities that their offers of help have been rejected.
He said the Government was willing to "work with any provider" who had the "right infrastructure and skills" and urged them to get in touch.
The minister also said he expects there to be 25,000 tests per day by the "middle of April".
Asked when the national coronavirus testing centre near Milton Keynes would be fully operational, Mr Jenrick replied: "I don't know precisely when that's going to be coming on board.
"Everything is being brought forward as quickly as it possibly can."
The promise of 25,000 tests per day by mid-April is in stark contrast to comments made by NHS medical director Professor Stephen Powis last Wednesday who said there would be "hundreds of thousands of tests" per day within the next few weeks.
