As many as 750,000 coronavirus tests have been recalled by their manufacturer after amid safety concerns, the Department of Health has said.
The UK's medicines and healthcare products regulator (MHRA) told producer Randox on Saturday to recall the kits which were sent out to both care homes and individuals.
But the Government said this was a precautionary measure, with the testing kits posing a low safety risk.
The results of Randox tests are still valid, the Department of Health added.
The news comes just weeks after Matt Hancock told Brits not to use Randox kits until further notice, with the health secretary calling the swabs "not up to standard".
A Department of Health spokesperson said on Saturday: "We have high safety standards for all coronavirus tests. Following the pausing of Randox kits on 15 July, Randox have now recalled all test kits as a precautionary measure.
"Our testing support for care homes continues as any resident or member of staff with symptoms can immediately access a free test and we are exploring ways to increase the amount of testing, making full use of available lab capacity."
Randox, based in Northern Ireland, claims to be responsible for up to 17 per cent of coronavirus tests carried out in the UK, and has sent out about 1.3 million tests so far.
The Department of Health has also told Randox to recall Randox test kits from NHS test and trace settings.
Randox said that the decision to recall the tests was because of a lack of EC certification - meaning they are not allowed to be used in the European Economic Area.
Randox said in a statement: "Randox Laboratories have today taken the decision to recall Covid-19 sample collection kits, following the identification of incomplete EC certification. On 15th July DHSC placed these kits on hold due to the absence of swab certification from an external supplier.
"To date, Randox have not been provided with evidence to satisfactorily support the CE marking for these swabs. So, noting the lack of CE certification by the supplier and that some kits remain in the field at this time Randox has, as a regulatory measure, initiated the recall of those kits used within the National Testing Programme."