Swindon Borough Council is asking the public to follow national NHS guidance over the covid testing controversy surrounding a Midlands lab.
Following reports of people receiving negative PCR test results after they have tested positive on a Lateral Flow Device, NHS Test and Trace has investigated.
The organisation has suspended testing operations provided by Immensa Health Clinic Ltd at its laboratory in Wolverhampton.
NHS Test and Trace estimates that 43,000 - mostly in the South West - may have been given incorrect negative PCR test results between 8 September and 12 October, mostly in the South West of England.
Dr Will Welfare, Public Health Incident Director, UK Health Security Agency (UKHSA), said: "We have recently seen a rising number of positive LFD results subsequently testing negative on PCR.
"As a result of our investigation, we are working with NHS Test and Trace and the company to determine the laboratory technical issues which have led to inaccurate PCR results being issued to people. We have immediately suspended testing at this laboratory while we continue the investigation.
"There is no evidence of any faults with LFD or PCR test kits themselves and the public should remain confident in using them and in other laboratory services currently provided.
"If you get a positive LFD test, it’s important to make sure that you then get a follow up PCR test to confirm you have covid-19. If you have symptoms of covid-19, self-isolate and take a PCR test."
The NHS insists this is an isolated incident attributed to one laboratory but says all samples are now being redirected to other laboratories. The number of tests carried out at the Immensa laboratory, the NHS says, is small in the context of the wider network and testing availability is unaffected around the country.
NHS TT is contacting the people who could still be infectious to advise them to take another test. Close contacts who are symptomatic will also be advised to take a test in line with normal practice. Anyone with symptoms is asked to book a PCR test. Those with a positive LFD test should get a follow up PCR test to confirm they have covid.
Andrea Riposati, CEO of Immensa Health Clinic Ltd, said: "We are fully collaborating with UKHSA on this matter. Quality is paramount for us. We have proudly analysed more than 2.5 million samples for NHS Test and Trace, working closely with the great teams at the Department of Health and Social Care (DHSC) and UKHSA.
"We do not wish this matter or anything else to tarnish the amazing work done by the UK in this pandemic."