A fatal heatwave with temperatures of up to 40C could kill thousands of people in Sussex, experts have warned.

A seriously hot summer between now and 2012 could claim more than 6,000 lives in south-east England, a Department of Health report claims.

The report says there is a one in 40 chance that by 2012 the region will see a severe heatwave due to climate change.

Such a scenario could cause 3,000 immediate deaths, and the same number of heat-related deaths throughout the summer. The elderly will be most at risk.

Temperatures could even outstrip the hot summer of 2003 in which temperatures soared to 38C and left 900 dead across the UK.

But council and health chiefs in Sussex today said they were well prepared for a prolonged heatwave.

Professor Robert Maynard, who chaired the panel behind the report, said: "Climate change is likely to be one of the major challenges that humanity faces this century.

"It is important that we assess the possible health impact and take any actions that could minimise the consequences. The publication of this report is a significant step in that process."

The panel of scientific experts commissioned by the Department of Health and Health Protection Agency (HPA) looked at the way the UK has responded to rising temperatures since the Seventies.

While summers in the Sussex became warmer between 1971 and 2003, there was no change in heat-related deaths.

The report's authors acknowledge that predicting heatwaves and their effects is difficult, but said: "in terms of conventional thinking about risks to health, a risk of one in 40 is high".

Kevin Claxton, resilience manager for Brighton and Hove City Teaching Primary Care Trust said: "We are aware of studies in climate change, understand the safety issues for our local population in a heatwave, and regularly review and update our heatwave contingency plan.

"That plan is put into action whenever a national heatwave warning is issued. It involves contacting partner organisations across the city, so they can activate their own plans, as well as offering advice to the public about how to stay safe and well".

A spokesperson for East Sussex County Council said: ìIf we were to experience a prolonged heatwave one summer, there is no doubt that we would be concerned for the health of our local population ñ especially our older residents.

"We would activate emergency plans, in partnership with the NHS, to ensure that people knew how to look after themselves.

"A lot of this is common sense such as drinking plenty of water and staying out of the sun, but we would also be asking people to check that their older relatives and neighbours were managing in the extreme heat.

"Our Adult Social Care department has details of people that would be classed as especially vulnerable in these circumstances, and our staff would be checking on them regularly."

An August 2003 heatwave in France killed a total of 14,800 people, according to official figures.

The unusually high number of deaths put a heavy strain on mortuaries following a fortnight of record-breaking heat.

A spokesman for West Sussex County Council said: "We have heatwave contingency plans in place just as we do for things like flooding and avian flu outbreaks.

"We update those once a threat appears to be greater and it includes advice we would give and what action needs to be taken. We are aware of this report but it has not caused us any concern as we are well prepared."

The report shows that even 6,000 deaths due to heat pales in comparison with the number of cold-related deaths, which in the UK currently average about 20,000 per year.