The Environmental Audit Committee has published a new report, Heatwaves: adapting to climate change, in which it makes a series of recommendations to help workers cope in overheating work environments.
These include a review of the building regulations for a new standard to prevent overheating in new buildings, as well as formal guidance from Public Health England to employers to relax dress codes and allow flexible working during heatwave alerts.
However, the recommendations have been branded an "unnecessary step too far" by IOSH.
S 7 of the Workplace (Health, Safety and Welfare) Regulations requires employers to maintain a "reasonable" temperature in the workplace. The minimum temperature is 16°C, or 13°C if work involves physical activity, however the regulations do not specify a maximum temperature.
The Health and Safety Executive's (HSE) website says: "A meaningful figure cannot be given at the upper end of the scale due to the high temperatures found in, for example, glass works or foundries. In such environments it is still possible to work safely provided appropriate controls are present."
In its Approved Code of Practice, the HSE recommends employers "take all reasonable steps to achieve a reasonably comfortable temperature" and advocates the use of fans and increased ventilation in extremely hot weather.
Overheating work environments can lead to heat stress, particularly for workers engaged in heavy outdoor manual labour and for employees working in offices built in the 1960s and 1970s as these tend to have poor ventilation systems, the report notes.
It says: "The risk of overheating is not adequately addressed in the building regulations and the wider regulatory framework. The health of occupants should be a key priority of the building regulations, especially as severe heat events have become increasingly common since 1950 and are set to become more frequent. The Committee on Climate Change has repeatedly recommended a standard or building regulation to prevent overheating in new buildings, however thermal comfort is still not addressed in the building regulations."
According to the Chartered Institute of Building Services Engineers, indoor temperatures that exceed 28°C for long periods are likely to result in reduced productivity.
Mary Creagh MP, chair of the Environmental Audit Committee, said: "Heatwaves cause premature deaths, from cardiac, kidney and respiratory disease. There will be 7,000 heat-related deaths every year in the UK by 2050 in the UK in the government does not take action."
TUC general secretary Frances O'Grady said: "The law only gives minimum working temperatures, but the hot summer we're having has shown the need for a maximum limit too. It's great to have support for MPs for this commonsense policy, and we hope the government will take quick action.
"Meanwhile we encourage employers to keep on being sensible while the hot weather goes on. Relaxing dress codes and being flexible on working times to avoid the hottest part of the day can make things much easier."
Duncan Spencer, IOSH's head of information and intelligence, said: "While it is important that employees are able to work in reasonable temperatures, introducing prescriptive legislation around maximum temperatures would be an unnecessary step too far.
"Employers are already legally obliged to ensure workplaces are not too cold or too hot. It is key to note that one size does not fit all, which is what we'd be looking at with the suggested legislation. Every workplace is different and every worker is different, in so far as what temperature they feel comfortable at. So, it comes down to completing a quality risk assessment and acting on its findings.
"Furthermore, employees have a responsibility themselves to ensure they aren't too hot. They can wear appropriate clothing, drink lots of water, take regular breaks and -- if possible -- move to cooler parts of the workplace."