Autistic schoolchildren treble to over 3,000

The report, published by the Scottish Executive, found that 3,060 children in schools had been diagnosed with the disorder, up from 820 in 1998.

Ministers and doctors insist that the more than threefold rise is entirely due to increased awareness and better diagnosis of the condition.

But campaign groups insist that the statistics reveal an "autism epidemic" which may actually be even higher than the statistics show.

The figures have been published as campaigners prepare to take their case to the Scottish parliament this week, calling for ministers to create a specialised autism treatment centre in Scotland.

Among others, the petition is signed by four doctors in Scotland who believe that Scotland should follow the United States in developing new methods for treating the illness.

Bill Welsh, director of Action Against Autism, said: "Despite claims that the increase is due to the widening of diagnostic criteria, recent studies suggest that this would account for less than 25% of the increase and that we have a genuine autism epidemic."

Up until now, medics have placed genetic factors as key to understanding why autism occurs, but campaigners are now urging further research into other factors - including the possible influence of the MMR jab.

The authors of a study claiming that the MMR jab is linked to autism have since issued a partial retraction, but there remains deep scepticism about its safety. Scotland on Sunday revealed earlier this month that a third of family doctors still had doubts about the safety of the MMR jab.

Those concerns have led to a drop in uptake, and a consequent rise in the number of mumps cases being recorded in the country.

The new figures are contained in the annual census of schoolchildren in Scotland. Of the 3,060 children registered as suffering from autism, the vast majority - or 2,669 - are boys.