Dominic Raab has warned the public that lockdown measures could last into June as ministers came under increasing pressure to set out a detailed plan to ease the stringent restrictions. Setting out plans for a minimum three-week extension to prevent a deadly “second peak” of infections, Boris Johnson’s stand-in said that any relaxation now would “substantially increase the number of deaths”. And dispelling any hopes that the conditions would be lifted entirely before the May bank holiday, he said that there could be ongoing local lockdowns well into the summer to avoid new hotspots emerging. Raab said ministers had received “very clear advice” from Sage, the expert scientific committee advising the government, that lifting restrictions now would risk a damaging second wave of infections, which would “substantially increase the number of deaths”. “It would undo the progress made to date, and as a result, would require an even longer period of the more restrictive social distancing measures.” His announcement came as ministers faced new calls to explain how they intend to control the virus so that the lockdown can eventually be relaxed – with one adviser, Neil Ferguson, breaking ranks on Thursday to call for a “single-minded emphasis on scaling up testing and contact tracing”. He said the government needed to accelerate action as it had with Brexit and argued that a huge infrastructure of testing and contact tracing would need to be in place in order for the lockdown to be lifted without further peaks. “Without that, our estimates show we have relatively little leeway. If we relax measures too much, then we will see a resurgence in transmission,” he told the BBC’s Today programme. Matt Hancock, the health secretary, reacted to the criticism testily, saying Ferguson “advises government. He is not in the government.” When pressed for a timescale on lifting restrictions, Raab pointed to Boris Johnson’s remark of a month ago, on 19 March, that it would take 12 weeks to “turn the tide” of the virus. “That, broadly, is the outline,” Raab said. The UK is now in its fourth week of lockdown. Raab set out five conditions that would need to be met before any loosening of the rules. These included a sustained fall in the daily death rate, and confidence that the supply of PPE and testing can meet future demand. In a rebuke to rightwing commentators arguing for the lockdown to be lifted to alleviate the economic costs of having businesses shuttered and workers furloughed, Raab added that “early relaxation would do more damage to the economy over a longer period”. Rather than lifting the restrictions, Raab talked of “adjusting” them, adding: “It could mean relaxing measures in some areas, while strengthening measures in some other areas”. A Downing Street source called the approach “keyhole surgery”. He stressed that while the infection rate had fallen in the community, “we have issues with the virus spreading in some hospitals and care homes”. Hancock promised more testing and protective equipment for care home staff on Wednesday, with many reporting inadequate supplies and haphazard advice from the government. The Labour leader, Keir Starmer, welcomed the extension of the measures. “I fully support the government’s decision to extend the lockdown,” he said. ‪“The priority now must be to ensure we see a ramp-up in testing, that staff get the PPE they desperately need, and that more is done to protect our care homes from the virus. We also need clarity about what plans are being put in place to lift the lockdown when the time is right.” Raab was deputising for the prime minister, who is convalescing at Chequers after being hospitalised with the virus. Downing Street said Boris Johnson was not involved in the decision to extend the restrictions, but that Raab had updated him by phone. One Tory MP said it was “rightwingers in cabinet and the wider party” who were pushing for an early exit from the lockdown, but that No 10 was highly cautious. A senior Westminster source with knowledge of the government’s thinking said they believed a move towards contact tracing conducted by an army of trained people was about to become “the next big U-turn”. Previous reversals of government policy include the acknowledgement of the need for mass testing, the abandonment of the herd immunity strategy, and the realisation that an antibody test was harder to develop than first thought. Another change of heart could be over the wearing of masks by members of the public. Chief medical officer Chris Whitty said this was “a very live issue that we are re-examining”. He said there was medical evidence of a “small” effect on the transmission of the virus. Advisers had previously suggested there was little benefit to wearing masks, but Whitty said: “The point about scientific advice is, it evolves.” The chief scientific adviser, Patrick Vallance, also hinted at ongoing measures, saying the challenge was to get R – the transmission rate of the virus – below 1 and keep it there. “There may be a number of measures that need to be continued to allow that,” he said. “There will be some changes that need to take place, around things like home-working.” Hancock will come under pressure to commit to a coordinated testing and contact tracing regime when he appears before a blockbuster select committee hearing on Friday, led by former health secretary Jeremy Hunt and attended by several other committee chairs as guests. Hunt has long been pushing for a mass testing and tracing strategy, which was dismissed by the government’s experts in mid-March when they moved from a policy of trying to contain the virus to trying to delay its peak. At that point, on March 26, Dr Jenny Harries said testing and contact tracing was “not an appropriate mechanism as we go forward”, despite the World Health Organization’s exhortation to “test, test, test”. The government has since conceded the point on mass testing and begun to develop an app that can help trace contacts. However, there are concerns that online tracing will not be effective at reaching older people, that it is voluntary, and that privacy concerns may hamper its usefulness.