Ministers have held a series of high-level meetings with trades unions and business leaders amid fears that millions of people will be too fearful to return to work as pressure intensifies on the government to publish a path out of the national lockdown. The Guardian has been told that both sides of industry have been drafted into seven sector-by-sector meetings chaired by the business secretary, Alok Sharma, in recent days – after concerns arose in Whitehall that many employees may be reluctant to return to the workplace, even when the government gives the green light. Measures under discussion include the use of face masks and hand sanitiser on public transport, one-in-one-out rules and socially distanced queues for non-essential shops, and revised operating procedures for building sites. Some construction projects halted as a result of the virus have already restarted. Boris Johnson urged Tory colleagues pressing for an immediate end to the lockdown to “contain your impatience” in a Downing Street address on his first day back at work on Monday, as the UK coronavirus hospital death toll passed 21,000. The prime minister said the country now had the opportunity to overcome Covid-19, but was at the “moment of maximum risk”. But he also pledged to “fire up the engines of this vast UK economy” as soon as it is safe to do so. No 10 previously had little time for either business groups such as the CBI – which it regarded as a hotbed of remainers – or the trades unions. Yet, since the onset of the crisis, both groups have been closely involved in drawing up chancellor Rishi Sunak’s economic rescue package – and they are now helping to prepare the ground for what Johnson called the “refining” of lockdown restrictions. While Tory donors and backbenchers have been calling for economic activity to resume as soon as possible, polling suggests strong support for lockdown measures remains, and government insiders pointed to so-called “over-compliance” with the restrictions already in place. When schools were ordered to stay open for key workers’ children, ministers expected perhaps a fifth of pupils to attend – but the actual figure has been just 1% as concerned parents have kept the vast majority at home. Getting schools up and running again – and persuading parents their children will be safe – is regarded by ministers as a necessary precondition for allowing many people to return to work. Schools are not expected to reopen fully until June, after the spring half-term. In a characteristically upbeat statement delivered outside Downing Street two weeks after he was discharged from hospital following intensive care treatment for coronavirus, Johnson compared the virus to “an unexpected and invisible mugger”. “This is the moment when we have begun together to wrestle it to the floor and so it follows that this is the moment of opportunity. This is the moment when we can press home our advantage. It is also the moment of maximum risk,” he said. He said it was too soon to say when the lockdown measures would be altered. Addressing those calling for an early lifting of the restrictions, he said: “I entirely share your urgency. It’s the government’s urgency and yet we must also recognise the risk of a second spike; the risk of losing control of that virus. “That would mean not only a new wave of death and disease but also an economic disaster and we would be forced once again to slam on the brakes across the whole country and the whole economy, and reimpose restrictions in such a way as to do more and lasting damage.” The government’s scientific advisers are working to model the potential impact on R0 – the infection rate of the virus – of lifting different restrictions. The chief medical officer, Chris Whitty, said on Monday it was not yet clear how much difference reopening schools would make, for example. He said the Sage committee of scientists, of which he is a member, would present ministers with estimates of the impact of various measures in the coming days – allowing the politicians to make decisions of how to adjust the lockdown. Echoing the language used by Dominic Raab, deputising for the prime minister, on Sunday, Johnson said the government would “refine” the stringent distancing restrictions imposed on 23 March, which are due to be reviewed by Thursday next week. Conservative campaign chief Isaac Levido is involved in the task of replacing the government’s “Stay Home, Protect the NHS, Save Lives” slogan with a more nuanced message for what Johnson repeatedly called the “second phase” of the crisis. Sunak disclosed on Monday that 4m workers had been furloughed under the government’s unprecedented job retention scheme, in which the taxpayer underwrote the costs of paying staff wages as they are temporarily laid off. He also announced the creation of a new loans scheme for the smallest businesses, which will be 100% guaranteed by the government. Johnson stressed his determination to build a consensus over future measures, saying he would include opposition parties in his deliberations. Keir Starmer, the Labour leader, has so far adopted a cautiously supportive approach to the government’s handling of the crisis, while pressing ministers on specific issues including testing and the availability of personal protective equipment for frontline health workers. Frances O’Grady, general secretary of the Trades Union Congress, said: “Protecting workers’ safety and rebuilding the economy must go hand in hand. “That’s why we have called on government to set up a national recovery council with unions and employers. Any business that refuses to put in place safe systems of work should face the threat of prosecution.” The health secretary, Matt Hancock, announced on Monday that some hospital treatment halted because of the virus, including cancer care, will now be progressively resumed. Presenting the daily Downing Street press conference, Hancock stressed that the NHS remained open, and urged the public to continue to make use of it as usual. Ministers are concerned that while it has suppressed Covid-19 cases, the lockdown is creating its own risks to public health because people are anxious about going to hospital with other conditions. “Our message is that the NHS is open: help us to help you,” Hancock said. He urged members of the public suffering chest pains, or who fear they may be having a stroke or heart attack, to use A&E.