Deluded Boris Johnson has doubled down on his boast that our underperforming Covid-19 contact-tracing system is “world-­beating” – as data proves it is getting even worse.

Figures for NHS Test and Trace, vital to our pandemic fight, showed yesterday that contacts reached fell from 51% to 46% in a week.

It comes days after a Lancet study concluded the figure needs to be at 68% by the time schools go back next month to avoid a deadly second wave in the winter.

Experts had wanted local health protection teams to do contact tracing – but the Government set up a central programme staffed on the cheap by outsourcing firms.

And yesterday, the boss of firm Serco was forced to defend his 10,000 tracers having only spoken to an average of 2.4 people each.

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But despite the damning data, bullish Mr Johnson repeated the claim he made at May’s launch.

He said: “If you look at what we are doing, I think… it certainly does fit that description of world-beating. We are testing more per head of population than virtually any other country in Europe, certainly, in America they are testing a huge number.”

The Government said that as of Wednesday, 46,413 had died in hospitals, care homes and the wider community after positive tests for Covid-19 – up 49 in a day.

Separate figures show 56,600 deaths registered with the disease mentioned on the certificate.

The Government also said there were 950 more lab-confirmed cases in the 24 hours to 9am on Thursday.

Without better contact tracing, experts warn of more shutdowns.

Labour leader Keir Starmer said: “We don’t need a world-beating track and trace system, we need an effective one and we haven’t got it.

“If this doesn’t work it’s difficult to see how we’re going forward.”

The calculation for 46% overall contacts took in data includ-ing the percentage of people who tested positive and were contacted, and how many contacts were reached.

Both of these fell, according to weekly figures for England to July 29. Test, Trace, Protect in Wales is doing better but does not publish such detailed data. Prof Chris Bonell, of the London School of Hygiene and Tropical Medicine, co-authored the Lancet study setting a 68% target.

He said: “The figures for England are disappointing. The system has been set up rapidly and that is an achievement. But rates of testing and tracing need to increase to avert a second wave.” Figures show while slightly more people came forward to record a positive test, few contacts are reached.

The study shows that women in particular suffered the most from anxiety and depression

Prof Keith Neal, an infectious diseases expert at Nottingham University, said: “One problem is one in five cases, who should be self-isolating, fail to be contacted despite multiple attempts.” Despite a slight increase in positive results, Office for National Statistics data suggests just one in six new Covid-19 infections each week are being tested.

Instead of beefing up existing local teams who have highly trained staff, the Government set up NHS Test and Trace for £192m with 20,000 call centre workers taken on via outsourcing firms.

The scheme’s troubles have led many local authorities to set up their own – including Greater Manchester, Sandwell council in the West Midlands, Blackburn with Darwen council in Lancashire, and Calderdale council, West Yorks.

Yesterday’s data showed that for cases handed to local officials, 98% of close contacts were reached – and Labour now wants local authorities put “in the driving seat”.

Health Secretary Matt Hancock

Serco chief executive Rupert Soames defended his operation after contact tracers on near-minimum wage deals described being “paid to watch Netflix ”.

He said: “If somebody rang you now and said, ‘Tell me everybody you have met, been in contact with, in the last 48 hours, give me their contact details’, how many do you think you’d be able to reel off?

“So there is an element of that and it is about 20% at the moment where people can’t remember or never knew the contact… the details of where they were.”

The outsourcing giant is among several firms recruiting, coaching and managing contact tracers.

Leaders of NHS Test and Trace say the dips are driven by a greater number of complex cases – e.g. those in care homes and hospitals.

The average number of contacts traced for each person who tested positive in the past week was 2.8, down from an average of 3.4 over the previous two months. Prof Sheila Bird, of Cambridge University, said: “Test and Trace’s poor performance in reaching identified close contacts of a non-complex index case needs explanation.”

But Tory Peer Baroness Dido Harding, in charge of the scheme, insisted: “NHS Test and Trace is working. It has already helped to prevent almost 250,000 unknowingly spreading the virus. But we do not work alone. Close partnerships with local government and local public health teams are essential.”

Meanwhile, Health Secretary Matt Hancock’s troubled contact tracing app may be scaled back.

It flunked a trial and could now only advise users of local Covid-19 levels, giving “risk scores” factoring in age, ethnicity and profession.

Working contact tracing apps have already been rolled out across Europe and in Northern Ireland.

Some 77.9% of those tested at a regional site or mobile unit in the week ending July 29 got a result within 24 hours. This was up from 76.4% the week before – but down from 90.8% in the week to July 1.

The PM had pledged results of all in-person tests would be back within 24 hours by the end of June.