Boris Johnson’s test-and-trace service has seen another fall in its contact-tracing rate as the number of people testing positive soared across England.

The figures for the week of September 17 to September 23 showed that just 71.6% of “close contacts” of Covid cases were reached by the system.

For the 14th week running, the figure is below the 80% figure that the government’s scientific advisers have said is needed to make the entire policy viable.

In line with the September surge in cases, NHS Test and Trace reported 31,373 people testing positive for the first time – a 61% week-on-week increase and four times as high as the number at the end of August.

But the service’s performance has gone backwards on the percentage of people it reached, dropping to 71.3% from 80.8% the week before.

And on the key proportion of the “close contacts” of those fed into the system – defined as someone who was less than two metres from someone with Covid for more than 15 minutes – just 71.6% were reached, down from 76.3% the previous week.

The news came as it emerged that Deloitte, a private firm used by NHS Test and Trace, was trying to sell its services to local councils. 

Testing turnaround times did improve, although they remain well short of the 100% target set by the PM for the end of June.

In the week to September 23, 38.1% of in-person tests – from local test sites, mobile testing units and regional test sites – were received within 24 hours compared to 28.2% in the previous week.

That still means that only four in 10 of such tests get results within the timeframe set by Johnson.

For all routes combined, 16.9% of tests from all test sites were received within 24 hours of a test being taken compared to the record low of 10.3% in the previous week.

Figures for home testing kits continue to be low, with just 2.9% of people in England receiving their result within 24 hours, up slightly from 1.8% in the previous week.

The stark difference in public sector and private sector contact tracing rates was once again highlighted.

For cases handled by local health protection teams, 97.6% of contacts were reached and asked to self-isolate, whereas the figure was 64.3% for cases handled either online or by private sector outsourced call centres.

Government insiders say that the low contact trace figures are explained partly by the shift from hospital and care home cases – termed “complex cases” – towards community transmission, where it is more difficult to identify and trace people.

The latest figures don’t take into account the launch of the NHS Covid-19 App, which aims to improve contact rates among people who don’t know each other.

Ministers prefer to use a different definition for contact tracing than Sage (the scientific advisory group for emergencies), highlighting those cases “where communication details were available”. On this measure, 83.7% were reached and asked to self-isolate up to September 23.

Shadow health minister Justin Madders said: “For the proportion of people being contacted to drop by nearly 10% in a week is appalling and really should not be happening at this point.

“Whilst some areas have improved, we are still a million miles away from the promise made by Boris Johnston back in June that the majority of people would have their test results back within 24 hours.

“And on the day it is revealed Deloitte, who are contracted by the Government to run test and trace, are trying to sell their contact tracing services to local councils, it is clearer than ever that their time would be better spent improving the huge issues in the existing system.”

However, health secretary Matt Hancock defended Deloitte, saying they “have done an incredible job in helping us to put together the contact tracing and the backward contact tracing that we have”. “Of course they should offer their services to local councils too,” he said.

29,037 people were transferred to the contact tracing system between
September 17 and September 23, a notable increase of 37% compared to the previous week.

The Department of Health and Social Care said the number of people transferred has been “notably increasing” since the beginning of August with over six times as many people being transferred in the most recent week compared to the beginning of August.

NHS Test and Trace boss Dido Harding revealed this week that former Sainsbury’s supermarket chief executive Mike Coupe is to take over as director of testing at the service from late October.

Sarah-Jane Marsh, an NHS official who apologised for delays to the public earlier this month, will step aside to make way for Coupe.

This is a breaking news story and will be updated. Follow HuffPost UK on Twitter, Facebook and Instagram.