The head of the NHS Test and Trace system has insisted it is working, despite more missed targets and the number of close contacts being reached falling to a record low.

Figures show the system has recorded the highest weekly number of positive tests since it was launched at the end of May.

A total of 9,864 new people tested positive for Covid-19 in England in the week to September 2, an increase of 43% in positive cases on the previous week.

But the statistics, published by the Department of Health and Social Care (DHSC) on Thursday, show just over two-thirds (69.2%) of close contacts of people who tested positive were reached through the system that week.

That figure is down slightly from 69.8% in the previous week, is the lowest weekly percentage since Test and Trace was launched and once again falls short of the Government’s 80% target.

Some 61.9% of people who were tested for Covid-19 in England in the week ending September 2 at a regional site or mobile testing unit – a so-called “in-person” test – received their result within 24 hours.

This is up from 53.3% in the previous week, but down from 63.4% in the week to August 12 and misses the Government target, with Prime Minister Boris Johnson having pledged that by the end of June, the results of all in-person tests would be back within 24 hours.

Local health protection teams continued to perform better in reaching contacts, with cases handled by them reaching 96.6% of contacts and asking them to self-isolate in the week to September 2.

By contrast, for those cases handled either online or by call centres, 61.3% of close contacts were reached and asked to self-isolate.

On a local level, the figures show just 42% of contacts have been reached for Test and Trace cases in Bradford handled online or by call centres – the lowest proportion for any local authority area in England.

For cases in Peterborough, 46% of contacts have been reached, for Blackburn with Darwen the figure is 48%, and for Kirklees and Nottingham the figure is 49%.

These figures are just for “non-complex cases” – cases handled online or by call centres – and cover the 14 weeks of Test and Trace from May 28 to September 2.

Despite the latest figures, Baroness Dido Harding, who is interim executive chair of the National Institute for Health Protection, said the system is working.

She said: “NHS Test and Trace is working and every week we consistently reach the majority of people testing positive and their contacts.

“We have now reached almost 360,000 people who may be at risk of unknowingly passing on the virus, helping to curb its spread.

“We are doing more testing for the British public than other comparable European countries and we are adding thousands more tests a day.”

But she made a plea to people without symptoms or those who have not been advised to get a test, saying: “For those who don’t have symptoms or haven’t been told they must have a test, we would please ask you to reconsider as it could be taking a test away from someone who really needs it.”

On Wednesday, Health Secretary Matt Hancock said there had been an increase in demand among people not eligible for tests in recent weeks.

DHSC said it was updating its guidance on testing eligibility on Thursday, to make it clear only those with symptoms or who have been asked to get a test should apply for one through the NHS system.