There should be a maximum temperature that business insurance customers can allow their premises to reach, it has been claimed.
According to the Trades Union Congress (TUC), the offices and factories of the UK's businesses insurance holders are likely to become more uncomfortable as summers become hotter through climate change.
The organisation suggested that the law is changed so business insurance customers are required to act if the workplace temperature reaches 24 degrees C and could be prosecuted if it hits 30 degrees C.
Brendan Barber, TUC general secretary, said: 'Even when the summers are bad, as last year's was, the temperature in some workplaces can be unbearable for employees and potentially dangerous in others."
The group added that hot offices can cause workers to suffer problems such as fainting, heat cramps, headaches, heat rashes and dizzy spells.
Mr Barber also called for the government to act before the full impact of climate change hits the UK.
According to NHS Choices, workers who have been affected by heatstroke should move to a cool area, have a cool drink and seek medical help.