An international team of specialists in tropical medicine say at least half a billion cases of malaria occur each year, nearly 50% more than current estimates by World Health Organisation (WHO).
The findings were published in the journal Nature, and point out that the WHO's reliance on clinical reports for its statistics does not include sufferers who did not seek treatment. Particular concern over the situation in south and south-east Asia was voiced.
Scientists from Kenya, Thailand and Britain said the threat from the deadlier form of malaria - due to the parasite plasmodium falciparum - had been hugely underestimated in the region. They have produced a map showing malaria hotspots, which should help the WHO campaign halve deaths from the disease by 2010.
"Getting numbers right is important", said Professor Bob Snow of the Kenyan Medical Research Institute in Nairobi, who is the co-author of the report. The Kenyan Medical Research Institute is one of the leading research institutes in Africa
The ability to to tackle the crisis is limited by not knowing the size of the problem, and how much money is needed to tackle it.
"This is particularly important for new drugs needed to fight malaria. These are expensive and difficult to produce," Prof Snow went on to say.
Richard Feachem, executive director of the Global Fund to Fight Aids, Tuberculosis and Malaria agrees, "Many believe that existing data grossly underestimates malaria, morbidity and mortality in Africa and Asia. We now have confirmation of this".
The WHO estimates the global incidence of malaria at about 300m every year, with 90% of cases occurring in Africa. The UN agency says more than a million people are killed by the disease each year.