UNION leaders have called for Britain’s bosses to ensure that workers are kept safe in the coming days after weather forecasters warned of extreme heat on the way. 

The Met Office issued a new-style extreme heat warning for the first time this week, with temperatures in some parts of Britain set to peak at 33°C. 

The warning, which covers parts of Wales, all of south-west England and other areas in south and central England, will remain in place until Thursday.