Even insecticidal shampoos to kill head lice raised the odds of the disease.

"The results ... support the hypothesis that various types of insecticide exposure may be a risk factor for childhood acute leukaemia," said Dr Florence Menegaux, of the research institute INSERM Villejuif, France, in a report in the journal Occupational and Environmental Medicine.

The researchers discovered the link after interviewing the mothers of 280 children who had been diagnosed with leukaemia and of 288 healthy children.

They found that youngsters exposed to fungicides and garden insecticides had more than double the risk of the illness than other children.

Leukaemia is the most common cancer in children. Symptoms include anaemia, joint pain and repeated infections. Children with the illness may also have nose bleeds and bruising without any apparent cause.

Chemotherapy, which is very effective against the disease, is the standard treatment.