Delays and problems with the contact-tracing system could leave England vulnerable to a rise in coronavirus cases as the lockdown is eased, NHS and public health groups have said. They were speaking after ministers finally acknowledged that a tracing app would not be ready by 1 June, when England is due to enter the next phase of lockdown easing with the reopening of primary schools and more businesses. Niall Dickson, the chief executive of the NHS Confederation which represents health trusts, said: “I’m not saying this is not going to work, but time is short. I would be nervous about a further loosening of the lockdown if we did it without being sure we had an effective test, track and trace system in place”. Concerns about tracing have been growing after a deadline for the rollout of the app, currently being tested on the Isle of Wight, was missed. A national rollout was initially promised by the health secretary, Matt Hancock, “in mid May”. Instead the tracing system will begin with 25,000 newly trained people based in call centres asking people who have coronavirus symptoms to list who they have come into contact with, so they can be traced and asked to self-isolate to prevent the disease spreading further. Asked when the app would launch, James Brokenshire, the security minister, admitted he was “unable to give you that definitive timeline”, but argued that it did not matter because the app was “only one part of the system”. Contact tracers, he said, would be able to reach 10,000 people a day if needed. However, experts say a functioning app – which works by tracking every other phone a person’s device comes into proximity with – would be useful to identify people at risk of catching coronavirus in many everyday situations. Keith Neal, emeritus professor of the epidemiology of infectious diseases at Nottingham University, said: “It is particularly useful where you don’t know people you are coming into contact with – on public transport or in the supermarket.” Members of the government’s Scientific Advisory Group for Emergencies (Sage) had a special briefing on Thursday on the status of the contact tracing system from Dido Harding, a Conservative peer who is leading the programme. One person who attended the virtual meeting said they believed the government had made “significant progress” but that the system was not yet complete. “This is an essential component in the monitoring system which is needed to enter the next phase of release from lockdown,” they said. John Ashton, a former regional public health director for north-west England, said it was not surprising the app was late because it represented “a completely untried technology”. Relying solely on human contact tracing from 1 June was “a big gamble and we may well see an uptick in case numbers”. However, Prof John Newton, from Public Health England, told the Downing Street daily press conference that the app was “distinct but compatible” with the human tracing system and there could be advantages in introducing one before the other. The app is being developed by a newdivision of the NHS called NHSX with the help of experts from the National Cyber Security Centre (NCSC), who acknowledged that it had been delayed while a number of errors were fixed. Ian Levy, the technical director of the GCHQ-backed organisation, said in a blog: “Due to the coronavirus pandemic, the app has been developed in very compressed timelines.” Separately on Wednesday, Apple and Google released software updates for their smartphone operating systems that laid the groundwork for their competing contact-tracing systems, which will be used in countries including Germany, Ireland and Italy. Updated phones now have a setting for “Covid-19 exposure logging”, which users can choose to turn on or off if their local health authority has opted in. In the UK, however, the choice is greyed out, with the text “not available in your region” presented instead. The discrepancy underscores the power Apple and Google have to ensure rapid adoption of contact-tracing apps that are built according to their specifications, which do not allow any data to be held in a centralised database. The UK government is insisting on using a centralised model, which retains information about who a person’s phone has come into contact with if they report feeling sick with coronavirus symptoms. NHS insiders say they have no immediate plans to abandon this approach even though it does not work as well with Apple- and Google-powered phones.