Boris Johnson will issue a sombre plea to the public to behave responsibly when pubs, bars and restaurants reopen in England on Saturday, warning them, “we are not out of the woods yet”. The prime minister will give a televised press conference on Friday, as the government struggles to strike a balance between protecting jobs by reopening key sectors of the economy and preventing a second wave of coronavirus infections. He will warn that customers who fail to abide by social distancing guidelines and other advice will be letting down their local landlords, hairdressers and cafe-owners – and could cause lockdown restrictions to be reimposed. “All these businesses and their workers have put in a heroic effort to prepare their venues for this reopening, to work out a way to trade in a way that keeps their customers safe. “But the success of these businesses, the livelihoods of those who rely on them, and ultimately the economic health of the whole country is dependent on every single one of us acting responsibly. We must not let them down,” he will say. “Just as when we first locked down, we will only succeed in reopening if everyone works together. Because we are not out of the woods yet.” Ministers opted to allow a swath of businesses, from hairdressers to hotels, to reopen on the same day, as part of a package of “easements” government scientists conceded were “not risk-free”. When the sweeping changes were announced last month, the chief medical officer for England, Chris Whitty, warned: “If people hear a distorted version of what’s being said, that says ‘this is all fine now, it’s gone away’ and start behaving in ways that they normally would have before this virus happened, yes, we will get an uptick for sure.” The body that represents A&E medics, the Royal College of Emergency Medicine, has issued a plea to pubgoers not to get “plastered” and overwhelm an already stretched health system. On Wednesday night, the Treasury deleted an upbeat tweet that urged the public to “grab a drink and raise a glass” because “pubs are back”, after it was criticised for being in poor taste during a pandemic that has claimed 43,000 lives in the UK. But ministers have been keen to see pubs and other hospitality businesses reopen, to help limit likely job losses in the coming months. The leader of the House of Commons, Jacob Rees-Mogg, said on Friday he had purchased a “yard of ale”, which he intended to drink in his local pub on Saturday night. “Last week, I suggested that people use a yard of ale to measure their social distancing, and I am glad to say that I have had a yard glass delivered. I am looking forward to visiting the Crown in West Harptree on Saturday to see whether I can get in the two-and-a-half pints that I believe a yard of ale contains,” he told MPs. “Whether I then drink the same is another question.” At Friday’s press conference, Johnson may be challenged about his father’s decision to travel to Greece this week. Stanley Johnson posted pictures on his Instagram account showing him arriving in Athens, and at an airport in a face mask. He told the Daily Mail he was “on essential business” to ensure a property he rents out was “Covid-proof”. Government advice currently urges the public against all but essential international travel. Asked about the journey on Thursday, the prime minister’s official spokesman said: “It is for individuals to make the judgments themselves.”