Experts fear that thousands of Brits may have been told they are coronavirus free because swabs used in tests did not go as deep into the nose as is needed.
The Government has rapidly stepped up testing across the UK and people can now get tested at drive-thrus or have them posted.
But, there are concerns that self-tests are less accurate as they use shorter swabs and do not need to be put as deeply into the nose.
Guidance for the test says: "No force is needed and you do not have to push far into your nostril". Professional swabs, however, take longer and obtain samples from deep inside the nose, which can be very uncomfortable for some people.
Read more on dailystar.co.uk