The use of Covid-19 test kits supplied by Northern Ireland firm Randox has been "paused" over concerns that they are not up to standard.
The decision was announced in the House of Commons by Health Secretary Matt Hancock yesterday.
The Government said all laboratories must pause the use of test kits produced by the Crumlin-based firm "with immediate effect and until further notice".
It said that some Covid-19 tests used as part of the NHS system had been temporarily stopped after they failed to meet safety standards. Mr Hancock told the Commons there had been a problem with swabs, but there was no suggestion test results were affected.
Mr Hancock told MPs: "We've identified some swabs that are not up to the usual high standard that we expect, and we'll be carrying out further testing of this batch as a precautionary measure.
"And while we investigate further, we're requesting that the use of these Randox swab test kits are paused in all settings until further notice.
"Clinical advice is that there is no evidence of any harm, the test results are not affected.
"There is no evidence of issues with any of our other test swabs, and there is no impact on access to testing."
Shadow secretary of state for health John Ashworth asked Mr Hancock what was wrong with the Randox test kits - and how many had been used.
"Is there a health risk to anyone who has been tested with these kits?" the senior Labour MP said.
"And how many people have these unsafe kits been used on and why weren't the certifications checked before these kits were used?
"These kits tend to be used in many care homes.
"We want care home residents to be tested regularly, we want care home staff to be tested regularly - can he guarantee that those care homes will now get alternative kits rapidly?"
Mr Hancock replied: "The reason is that they had a CE stamp and upon investigation of the certification of that stamp, the certification was not forthcoming, and therefore physical checks were done and we found that the swabs weren't up to the standards that we expect.
"This is limited to the Randox element of the testing system, not the broader testing system that we have.
"And I explained the clinical position, which is that there is no evidence of any harm having been done and that there is full access to testing because we have plenty of other test kits available."
A statement on the Randox website said: "As an immediate precautionary measure we have temporarily suspended distribution of home sample collection kits using one particular batch/supplier of swabs.
"This is a temporary measure and does not apply to our private business, which uses a different supplier of swabs.
"Test results from Randox kits are not affected."