Autism is now so over-diagnosed that within 10 years there will be no difference between someone with the condition and the average non-autistic person, experts have warned.

Rates of autism are rising, with between one and two per cent of western populations diagnosed with the disorder.

One in 100 Britons is now considered to be autistic, around a twenty-fold increase from the 1960s, and some scientists are investigating whether the rigours of modern life are to blame.

But a new study by the universities of Montreal, in Canada, and Copenhagen, in Denmark, has found that the bar for diagnosing autism has become progressively lower in the past 50 years.

If the trend continues, those with the condition will become indistinguishable from people without it by 2029, the researchers estimate.

Professor Laurent Mottron, of the University of Montreal’s Department of Psychiatry, said: “If this trend holds, the objective difference between people with autism and the general population will disappear in less than 10 years.

“The definition of autism may get too blurry to be meaningful - trivializing the condition - because we are increasingly applying the diagnosis to people whose differences from the general population are less pronounced.”