With temperatures predicted to hit 32C today, firms are being encouraged to let staff wear casual clothes such as shorts and vest tops to work.

The call has come from the TUC, which says bosses who drop the strict dress code during the heatwave and allow employees to ditch the jackets and ties will get more out of staff in return.

The union organisation points out that while there is a legal limit for working in cold temperatures (16C), there is no upper limit to help workers feel comfortable in sweltering conditions.

TUC general secretary Frances O'Grady said: "It's no fun working in a baking office or factory and employers should do all they can to take the temperature down.

“Clearly vest tops and shorts are not suitable attire for all frontline staff, but those not dealing with the public should be able to discard their tights, ties and suits.

"Extreme heat can be as unpleasant to work in as extreme cold, and so long as the UK has no legal maximum working temperature, many workers will be working in conditions that are not just personally unpleasant, but will also be affecting their productivity.”