The coronavirus test and trace system was condemned as “barely functional” today as its tsar admitted that demand was up to four times capacity, while 90% of tests were failing to hit the 24-hour turnaround target. The Guardian has seen documents showing tracers taking up to two weeks to contact friends, relatives and workmates of people diagnosed with Covid-19 – the entire length of the self-isolation period. But amid growing anger and lengthening queues at testing centres, Dido Harding, head of the £10bn NHS test-and-trace programme designed to prevent a second wave of Covid-19, told MPs on Thursday: “I strongly refute that the system is failing.” It came as sources said Leeds and Lancashire were expected to face enhanced lockdown measures, bringing the number of people subject to restrictions to more than 11 million, including nearly 2 million in north-east England. Official figures confirmed a 75% increase in positive weekly cases across England last week. Just 1.9% of people using a home test kit in England got their results within 24 hours in the week to 9 September, according to official figures – the lowest percentage since test and trace was launched in May. Results from 33.3% of in-person tests were turned around within 24 hours, down from 66.5% the previous week, creating knock-on delays for contacts required to self-isolate. Harding, who also heads the newly created National Institute for Health Protection, told MPs: “We made a conscious decision because of the large increase in demand to extend the turnaround time in order to process the number of tests in the last couple of weeks.” She admitted that demand for coronavirus tests across the UK was three to four times higher than the total daily capacity of 240,000 – 82,000 in the NHS and Public Health England and 160,000 in the community. It means that requests for tests could amount to nearly 1m a day, based on estimates including the number of people calling 119 and visitors to the government website, though “there will be some double counting in that”. Harding promised numbers would now be published daily. Surveys outside the testing centres found that 27% of people turning up did not have at least one coronavirus symptom as stipulated, she said. Asked by Greg Clark, chair of parliament’s science and technology committee, whether she was saying that 27% were lying, she said that those who arrived on foot at a local centre without an appointment had not made such a claim. “I completely understand why people are worried and scared,” she added. The Guardian was told that, in a number of cases, contact tracers working for one firm hired by the government to ensure close contacts of confirmed Covid cases are tracked down and told to self-isolate have called the contacts only to discover that they were first identified as being at risk up to 14 days earlier. One contact tracer said: “Some people are being told by test and trace that they need to self-isolate when their isolation period has been and gone. I rang someone a few days ago to tell them that they were a contact of a confirmed case and therefore needed to self-isolate. But halfway through the call I realised that her self-isolation period began on 31 August.” Test-and-trace records relating to contacts appear to confirm the tracers’ claims. Munira Wilson, the Liberal Democrats’ health spokesperson, said the UK’s testing system “seems barely functional” and added: “The testing system is in meltdown. People can’t access tests, turnaround times are down, cases are rising. The government is at risk of losing control of the virus.” Prof John Ashton, a former regional director of public health for north-west England, said the performance of the system was so poor that it could lead to legal claims against the authorities. After seven or 14 days with self-isolating, “the horse has bolted – they have already spread it,” he warned. “If people sicken and die, and it spreads to people who it shouldn’t affect because we should have been more on top of this, we are looking at gross negligence.” In a further blow, it is claimed that part of the software system used by a contact tracing firm when dealing with known carriers’ contacts has been malfunctioning this week, limiting the amount of work it can do. The firm has told some contact tracers to refresh their computer screens only every five minutes as it cannot cope with more regular use, documents suggest. Some contacts have become so exasperated by the length of time a call takes that they have hung up, tracers said. The Department of Health has been contacted for comment. One woman with confirmed Covid-19 provided four contacts to the national contact tracing system, but said that nine days after she tested positive, three of them had not been contacted. The one that has is her husband, who lives with her. “It’s a shambles,” said Rosie Allan, who had been on a weekend break at a Somerset hotel with friends, all of whom subsequently tested positive. “It’s going to be much better if people get in touch with their contacts themselves. It is obviously not world-beating.” She said she was contacted by a call centre two days after her positive test and it took the operator around 40 minutes to gather the details of four people. He took the phone number of one of them, accepting names and addresses for the rest. The 18,371 people who tested positive for the virus between 3 and 9 September is the highest weekly number since test and trace was launched at the end of May. The latest progress report showed that 14% of tests delivered a result in under 24 hours in the week to 9 September, down from 32% a week earlier. Jeanelle de Gruchy, president of the Association of Directors of Public Health, said on Thursday that her colleagues around the country were reporting “slow or inadequate” contact tracing. “We all want and need it to improve fast,” she said in a call for urgent funding for local public health responders. “The situation is simply unsustainable. We cannot keep our communities safe on a shoestring. An emergency funding package for local outbreak prevention and management is now urgent – we need more people in our places and money into our councils to get the work done.” In a Commons debate on new restrictions imposed on nearly 2 million in north-east England because of rising infections, Jonathan Ashworth, the shadow health secretary, criticised Matt Hancock over the widespread unavailability of tests. He reminded Hancock that in May he had assured MPs that a big expansion of the capacity to test anyone aged five or over meant that “we have ‘now got testing for all’”. Ashworth added: “Yet four months later, for the British people, it has become not so much test and trace, more like trace a test.”