The Lowy report said early modeling predicted malaria prevalence could be 1.8 to 4.8 times greater in 2050 than 1990. The share of the world's population living in malaria-endemic zones could also grow from 45 percent to 60 percent by the end of the century.

By 2085, an estimated 52 percent of the world's population, or about 5.2 billion people, will be living in areas at risk of dengue.

It also said diseases will spread once climate change forces people to flee their homes, such as low-lying islands or coastal land swamped by rising sea levels.

For example, in the Pacific nation of Tuvalu, a ring of nine Polynesian islands, several thousand people have already left for New Zealand to restart their lives because of rising seas.

"The number of environmental refugees as a whole may reach 50 million by 2010, with small, low-lying island populations at the greatest risk. Displaced people from lowland areas could well provide the human reservoir for the spread of malaria and dengue," said the report.

"Global climate change will intensify the already significant malaria and dengue problems in maritime Southeast Asia and the Pacific Islands," said the report.

"Those countries with the fewest resources and poor public health infrastructure are likely to feel the impact of increasing disease the most acutely," said the report.

Up to half a billion new cases of malaria and as many as two million deaths, mostly children, are recorded each year. There are an estimated 50-100 million cases of dengue fever annually and approximately 25,000 deaths.

Indonesia had an estimated 6 million to 15 million registered malaria cases in 2005 and it is estimated that almost half of its population of over 225 million people will eventually be at risk from malaria due to climate change, said the Lowy report.

Australia, free of malaria and dengue fever, is also at risk because it is a "fringe country" to the expanding endemic zone of mosquito-borne diseases to its north, said the report.

"Mosquitoes are very sensitive to changes in climate. Warmer conditions allow the mosquitoes and the malaria parasite itself to develop and grow more quickly, while wetter conditions let mosquitoes live longer and breed more prolifically," it said.

"The sting of climate change is an international public health crisis being felt on Australia's tropical doorstep. It may soon be pressing on Australia's northern shores as well."

Climate change also threatens to increase the spread of dengue fever. The South Pacific's scattered island nations of Samoa, Tonga, New Caledonia, Kiribati, New Caledonia and Palau are currently struggling with an endemic of dengue, with more than 2,000 cases so far recorded in 2008.