An additional 263 people – 3.8 per cent – could not be reached at all because no communications details were provided for them.

Overall, since the start of the programme 113,925 people, representing 88.6 per cent, were identified as recent close contacts and reached through the contract tracing system out of 128,566 people reported.

Prof Keith Neal, Emeritus Professor of the Epidemiology of Infectious Diseases, University of Nottingham, said the number of people believed to be Covid-19-positive is much higher than that indicated by the number of tests, meaning more needed to come forward for testing.

“There are a number of issues currently with the system – these can only be sorted by members of the public as it requires individuals to take the appropriate actions to reduce spread,” he said.

Professor Neal added: “One in four positive people can’t be contacted – this is surprising and worrying – these people need to provide details to get the result of their test and they have a responsibility to be contactable, they should anyway be isolating at home so easy to get hold of.

“There has been a drop in the percentage of contacts who have been contacted from 90 per cent to 80 per cent, but this is still not a bad figure.”

Baroness Dido Harding, the executive chair of NHS Test and Trace, said: “In just three weeks, NHS Test and Trace has already reached more than one hundred thousand people who may have otherwise unknowingly spread the virus.

“The strength of NHS Test and Trace lies not just in our thousands of trained tracers, but in the public playing their part – providing us with the vital information we need to stop the spread of coronavirus, protect our families and communities, and ultimately save lives.

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