Companies are being threatened with prosecution if they do not make premises “COVID secure” for returning workers.
The warning comes as people in England are told to go back to work from Wednesday if they cannot do their job from home – such as builders and manufacturers.
Ministers have stressed firms should ensure social distancing stays in place as the lockdown is slowly eased over the next few months to stop the spread of coronavirus, which has already killed 32,692 people in the UK.
Best practice plans have been drawn up by the government for businesses to ensure workers are protected – such as remaining two metres apart, being given face masks or provided with hand sanitiser.
But the Health and Safety Executive (HSE) – which will do spot inspections to make sure firms are keeping people safe – has confirmed any that don’t follow the new rules could face legal action.
Chief executive Sarah Albon explained how much power the agency will have to live up to Prime Minister Boris Johnson’s demand for any reopening workplace to be “COVID-secure”.
At Downing Street’s daily coronavirus briefing, she said: “Inspectors can require businesses to do certain things – enforcement notices, requiring them to take particular kinds of action.
“In the most extreme circumstances if there is a risk of serious injury to an individual employee they can issue a notice which prohibits certain activities from taking place.
“Breach of those kind of enforcement notices is essentially a criminal offence and we can prosecute people who fail to do the right thing.”
Unions have endorsed the guidelines, TUC general secretary Frances O’Grady saying on Monday they are a “step in the right direction”.
She urged: “All employers must now carry out and publish risk assessments in consultation with unions and their workforces.
“After the confusion of the last few days, working people will only feel confident if government and employers act now to make safer working a reality in every workplace.”
The HSE has been granted a 10% budget increase to spend on equipment, hiring more call centre staff and carrying out more inspections.
Despite the lockdown changes in England coming into effect on Wednesday, the same measures are remaining in place in Wales, Scotland and Northern Ireland.