Siestas are popular in continental Europe

Met Office research has predicted by the second half of this century summers like the one in 2003 which killed thousands will become the norm.

Professor Bill Keatinge, a University College London expert on how heat affects the body, said midday rests would be needed to help people cope.

He said without a lifestyle change, the UK could see more people die of heat.

The 2003 heatwave - the hottest summer for 500 years - was linked to 27,000 deaths across Europe, including 2,000 in Britain.

2003 was a foretaste of thing to come if we carry on emitting greenhouse gases

Peter Stott, of the Met Office

During the average summer, 800 people in Britain normally die because of the heat - most commonly through heart attacks or organ damage as the body heats up.

But officials from the Met Office's climate research unit have predicted the UK could have summers as hot as 2003 - when temperatures hit 35ºC (95ºF) - every other year.

The study which is yet to be published analysed how climate change would affect temperatures and concluded the hottest days could rise by 7C to top 40C (104ºF).

Researcher Peter Stott said: "2003 was a foretaste of thing to come if we carry on emitting greenhouse gases. It is likely to become the norm."

Already this summer temperatures in Spain and Italy have been nudging 40C, prompting reports of heat-related deaths.

Change

Professor Keatinge said a change in habits was needed if temperatures do rise.

"When it is really hot people need to take precautions, especially the elderly. This means avoiding physical exercise, staying out of the heat.

"Siestas are a good way of doing this, even in central Europe such as Germany they are becoming more common with people working later.

"It is a simple way of staying cool without installing air conditioning."

Professor Keatinge also said people should eat and drink more during heatwaves.

Mark Gibbs, a Met Office official who advises the NHS on how to prepare for heatwaves, agreed lifestyle changes were needed.

"We need to look at these countries that have already adapted to the heat... building design, changing lifestyle."