Malaria is killing almost twice as many people around the world than was previously thought, a study has shown.

More than 40 per cent of the victims are older children and adults, challenging the belief that the vast majority of deaths occur among the under-fives.

The infectious disease claimed 1.2 million lives worldwide in 2010, according to the new research. This is nearly twice the number cited in a report from the World Health Organisation published last year.

The scientists, led by Dr Christopher Murray, from the Institute for Health Metrics and Evaluation at the University of Washington, analysed all available data on malaria mortality from 1980 to 2010.

Their findings, published in The Lancet medical journal, showed consistently higher death tolls than those in the 2011 World Malaria Report.

Worldwide, 433,000 more people over the age of five had been killed by malaria than World Health Organisation estimates suggested.