Experts are calling for more research into the causes of childhood leukaemia.
Experts are calling for more research into the disease
Doctors have made significant advances in treating the disease over the last 40 years, and far fewer children die from it.
But a conference in London on Monday will be told far less progress has been made in identifying what causes the disease.
The meeting has been organised by Children with Leukaemia, a leading national charity.
It will consider research on potential risk factors for the disease.
'No need to panic'
Michel Coleman, Professor of Epidemiology and Vital Statistics at the London School of Hygiene and Tropical Medicine, told BBC News Online: "There is evidence of an increase in the incidence of childhood leukaemia
"We have become steadily better at treating childhood leukaemia - at least in the sense of preventing children dying from it - but we have made little or no progress in preventing it.
"Rational approaches to prevention are difficult to formulate when so little is known about the cause."
He said that between 480 and 500 children under the age of 15 are diagnosed with leukaemia in Britain each year. Around 100 die from the disease, which accounts for about a third of all cancers in children.
The number of new cases diagnosed annually has risen over the least 40 years, particularly in children under the age of five.
Professor Coleman said the rate had increased from 64 cases per million children aged one to four in 1971 to 80 per million at the end of the century.
"Suggestions that part of the increase has been due to more children surviving infancy to reach the peak age of leukaemia incidence (one to four years) and to improved registration and diagnosis of the disease, may be partly true, but they cannot plausibly explain the overall pattern of data now at our disposal," Professor Coleman said.
But he added; "Parents should not panic. This is still an uncommon disease."
However Ken Campbell, of the Leukaemia Research Fund, challenged the figures.
He told BBC News Online: "There is no robust data to demonstrate beyond doubt that childhood leukaemia has increased in this country."