Brits should be sent home if workplaces get hotter than 25C, a union has demanded as a life-threatening 40C heatwave descends tomorrow.
The GMB said a “maximum working temperature” should be set at 25C in law, forcing bosses to take mitigating measures like air conditioning.
Chiefs also urged flexible working and dress codes, extra breaks and access to water - as Britain has a legal minimum temperature but not a maximum.
The Trades Union Congress (TUC) also wants a “new absolute maximum indoor temperature” though it would be set slightly higher at 30C, or 27C for those doing strenuous jobs.
The TUC would also change the law to force employers to try to reduce temperatures once they get above 24C and workers feel uncomfortable.
Tory Kit Malthouse urged bosses to consider letting staff work from home tomorrow and Tuesday - when the Met Office has declared its first ever red extreme heat warning and a ‘national emergency’ in England.
The Cabinet Office minister convened a Cobra meeting last night with the next one expected on Monday as trains are expected to ‘go slow’ to avoid tracks buckling.
But Boris Johnson - who is having a farewell party in his country retreat Chequers - did not turn up.
The Mirror understands at least some civil servants have been told to work from home if they can, including if the heat makes commuting unviable.
But there is not a single order across government for all civil servants to work from home, and key Downing Street and Cabinet Office staff working on the heatwave will be coming in.
A senior government source said: “People can make a call based on what’s right for them and their teams. This is going to be serious and dangerous heat.” Teams are being directed to the public health advice and relevant travel for their area.
Deputy Prime Minister Dominic Raab said working from home is “for employers to consider and for people to decide.”
He told Sky News: “Obviously we’ve got more flexible working, it’s one of the things after the pandemic lots of businesses are doing, so that will also help with this kind of thing.”
But Mr Raab rebuffed calls to shut schools, saying they should “make sure young children get the education they need.”
Tracy Nicholls, chief executive of the College of Paramedics, warned people could die in the heatwave - and there is a concern ambulance services will “tip over” in the longer term.
She told Sky News’ Sophy Ridge on Sunday: “It's difficult not to call it a crisis - it's been a stealth crisis.”
She added: “It's not that people aren't going to turn up. It's just that the system is not enabling paramedics, emergency department staff to do exactly what they want to do, which is look after everybody.”
Warning Brits over the heatwave she added: “This isn't like a lovely hot day where we can put a bit of sunscreen on and go out and enjoy a swim and a meal outside.
“This is serious heat that could actually ultimately end in people's deaths because it is so ferocious. And we're just not set up for that sort of heat in this country.”
TUC General Secretary Frances O’Grady said: “Working in sweltering conditions can be unbearable and dangerous.
“Bosses must make sure workers are protected with regular breaks, lots of fluids, plenty of sunscreen, and the right protective clothing for those who work outdoors - or relaxed dress codes for those working in shops and offices.
“And employers must give staff the chance to work flexibly so they avoid the hottest hours of the day and the stifling conditions of the rush hour commute.
“Anyone worried about their working conditions should join a union, it’s the best way to stay safe at work and make sure your voice is heard.”
Lynsey Mann, GMB Health and Safety officer, said: “Bosses need to do everything possible to keep workplaces cool, and more importantly, safe."
The 40C heatwave shows climate change “really is a risk to health”, the Deputy Chief Medical Officer warned today.
Thomas Waite said: “The scientific and medical communities are nearly in unanimous agreement that climate change really is a risk to health and we need to take carbon reduction and adaptations seriously.
“The thing that means for events like this is that the risk of this extreme heat is going up.
“So we all need to sort of think about the steps we can take during extreme weather for how we avoid getting ourselves into trouble in the first place.”
NHS Confederation chairman Lord Adebowale said health staff “are pretty stretched at the moment”.
He added: “Ambulances are operating at their peak, the waiting times for ambulances are now getting longer.
“We are going to be really, really pushed and it's not just the red warning, the heatwave - we are dealing with Covid, which is causing sickness in our ambulance crews.”
