The business secretary, Kwasi Kwarteng, has said companies must redouble efforts to ensure employees work from home unless their work is critical and cannot be done offsite, as the TUC urged the government to step up enforcement. Calls are growing for the government to rethink allowing construction sites to continue as normal and to permit only those whose operations are vital, with several industry employees telling the Guardian that safe practice has become impossible on sites. The government is preparing to ramp up warnings to employers that they must ensure they are making every effort to keep employees at home. Speaking to the Guardian, Kwarteng said there were “deeply troubling” reports of some businesses’ tactics to get employees into the office. “The vast majority of businesses have moved heaven and earth to protect the health and welfare of workers in what has been a truly difficult year,” he said. “However, recent reports that a small minority of firms have threatened employees with unpaid leave unless they come into the office are deeply troubling.” Kwarteng, who took over Alok Sharma’s brief in the business department after Sharma was made full-time president of Cop26, is understood to have repeatedly stressed the need for home working in introductory calls with business leaders over recent days. “The scientific evidence is clear that the next few weeks will be a critical time of the pandemic, so we need all employers to act responsibly and take every possible step to enable and support their staff to work from home,” he said. “The law is also clear that people must work from home unless they cannot reasonably do so. With the vaccine rollout accelerating, the end is in sight. But in the meantime it is vital everybody plays their part to protect our NHS and save lives – and I want to see British businesses leading from the front.” In the latest data released by the Office for National Statistics, 51% of the UK workforce were working at their normal place of work and 32% were working remotely. In April last year during the first lockdown, 46.6% of people said they were at least partially working from home. According to the ONS, the proportion of the workforce on furlough was 14%, roughly half the figure in mid-May. The data covers two weeks up to 27 December, and so not the current national lockdown in England. On Wednesday, the transport secretary, Grant Shapps, voiced concern about the number of people travelling on weekdays, revealing that Department for Transport data showed road traffic in Britain at 63% of pre-pandemic levels and bus usage outside London at 26%. It suggests car usage has almost doubled since the first lockdown, when it was about 32%, and bus usage has more than doubled. The problem appears particularly pronounced in London, where the most recent Transport for London data suggests tube travel is more than three times higher than in the spring lockdown. Underground journeys were at 17% of normal demand on Wednesday, compared with 5% in mid-April, and bus journeys were at 30% of normal demand. The City of London Corporation urged workers in the Square Mile to report their bosses if they are being forced or pressured to come into work. Its health and environment committee chair, Keith Bottomley, said firms should “think carefully about whether they truly need to be at their workplace”. Recruitment firms have been among the worst offenders, accounting for nearly a quarter of the 16 complaints lodged with the corporation against office-based firms since Christmas. Employers have given a raft of excuses for breaching guidelines, including that some staff are new, need supervision and therefore cannot work remotely. The corporation said none of the complaints were linked to overcrowding in offices, but stressed that businesses must take “every possible step” to allow staff to work remotely during the health crisis. “Extra consideration should be given to those people at higher risk,” it said. The TUC general secretary, Frances O’Grady, said it was time for the government to step up enforcement of home working and safe workplaces. She said: “With fewer people working from home than in the March lockdown, it is more important than ever that workplaces are safe, not breeding grounds for Covid-19. But many workers are still being forced to work indoors without adequate ventilation or proper social distancing from colleagues or customers. The government must urgently update the rules to keep pace with the latest science on the spread of the virus.” O’Grady said it was staggering that not one company had been prosecuted and fined for breaching official safety guidance. “Rather than lecturing the public on non-compliance, ministers should be cracking down on bosses who play fast and loose with workers’ safety,” she said. Construction sites and estate agents have been among the workplaces where MPs and unions have raised concern about staff. Responding to a Guardian callout, one estate agent working for a major firm said it was appalling that the property market was fully open. “The government’s stance is to stay home and not to go out unless it’s vital. How is browsing homes vital at this time?” the estate agent said. “Many agents and staff are concerned about getting infected but they can’t stay home as the government is allowing them to work, so no furlough. I know that would mean me losing money but I care about the situation.” A West Yorkshire site manager for one of the UK’s largest construction companies said senior managers were able to work safely from home while putting staff safety at risk. “I have had to send workers home who have come to work trying to hide symptoms as they do not want to miss out on pay,” the site manager said, speaking on condition of anonymity. “Projects have been brought forward to take advantage of the quieter roads, because we should be staying at home. Because of the mixed messaging the construction workers have received, there is definite complacency on sites … construction workers are being told to go to work, keep apart where you can and not to wear face coverings the majority of the time.” Another construction project manager wrote to the Guardian on Monday saying their work continued at pre-Covid levels, with 500 people on site, mask-wearing discouraged and no adequate ventilation. “Many are low-paid, with no job security and no incentive to self-isolate or report symptoms for fear of loss of income,” they said. “The job is for a major developer that can well afford to delay the completion of the project.”