Three years ago, Thrower gave up his job as a transport planner to look after Oliver and be a "house husband" while his partner continued to work full time. Aged 49, he is remarkably fit and energetic for someone whose son's hyperactivity ensures that he rarely gets an uninterrupted night's sleep. He spends all his spare time researching the causes of autism and its prevalence after discovering, to his amazement, that there was almost no official data. "Don't make it a sob story," he says genially: he doesn't want this to be a sentimental tale of a broken-hearted man. Looking at the yards of files in his office, you marvel that he managed to research and write the meticulous 90-page document on the possible causes, treatment and rates of autism that he presented to the health select committee of the House of Commons last summer.

Since the outset of his research, Thrower has been writing to ministers and officials at the Department of Health. At first they responded at length. "All propaganda and sales talk," says Thrower. But as his questions became more probing, the replies became more evasive, and now he doesn't get replies at all.

Undeterred, he ploughed on, and earlier this month produced his latest findings, which expose dramatic rises in autism and the shambolic state of data collection in the UK. As psychiatrist Dr Lorna Wing, an expert on autism, made clear in a recent report for the National Autistic Society: "There is no central recording by the UK government and very few epidemiological studies on which to make informed predictions. The available studies into this population are infrequent, expensive and problematic."

Thrower, alone in his study, in his own time and at his own expense, has made a start. Last year, he wrote to 161 organisations - every health authority in this country and a number of other bodies - asking them whether they collected data on rates for autism spectrum disorders (ASD - the technical term for wide-ranging autistic diagnosis) and what the data showed. Just over half replied. Thrower doesn't pretend that his monitoring was perfect. It was a trawl providing "interesting" snapshots. "Interesting" is his word: many people would say alarming.

Of the half who replied, only 17% had any detailed data at all, 38% had very limited data or were just beginning to think about setting up monitoring systems and the remaining 45% had no data whatsoever and no plans to gather it.

Thrower's research reveals that rates in some districts are far higher than the already high national prevalence rate of one in 100. In East Surrey, for example, where an audit was taken of all three-year-olds in a health trust district, autism amongst three year old boys was running at 1 in 69. Several authorities were uncertain as to whether the climb in reported cases of ASD was due to better diagnosis or greater prevalence, but a significant number believed it to be the latter. Thrower's analysis of statistics from Bromley Autistic Trust shows that in the 80s they had a 120% rise, with latest figures - for the early 90s - showing that rise continuing.

In the Birmingham Children's Hospital NHS trust there was an average annual increase of 37% of children under five during 1991-6. In Shropshire, the health authority figures show that while numbers are small they are rising, from 1-2 new cases per year in 1991 to 4-5 in 1999. In North Staffordshire, the health trust does has not have exact data but "has noted a bulge of younger cases in a local school", and in South Staffordshire the "special school for autistic children has had to expand provision and is still bursting at the seams".

Of the health authorities that have made the effort to collate information on autism rates, there is a huge variation in the effort made: West Surrey concluded that autism was very rare on the basis of a week-long survey in 1998; while Ealing Hammersmith and Hounslow uses data from hospital admissions.

Wakefield metropolitan district council's education department had done its own research. It found that until 1992 there were only four or five autistic children within its boundaries, but that "we now have 111 children diagnosed.

Local diagnosis is rising, particularly among younger children." The department adds that of the local education authorities questioned for the report, 31 say numbers amongst pre-school children are "rising rapidly". Yet according to Lorna Wing, "although substantially more children are now being diagnosed as having an autistic disorder, there are still far too many who are missed".

Thrower isn't seen as a lone nutter: far from it. The NAS says: "The disparities between neighbouring authorities revealed in Mr Thrower's findings highlight the critical need for a central initiative to establish reliable prevalence rates, and service needs." This seems to be a restrained way of saying: "What has Thrower stumbled on here?"

Something is beginning to give. Three weeks ago there was the first meeting of the new all-party parliamentary group on autism, chaired by Thanet South MP Stephen Ladyman, who says it was Thrower and other parents who kick-started this new committee. When first alerted to the issues, Ladyman discovered that not only was there no government data on autism, but, "The government didn't know it didn't know." Oliver Thrower's problems are tragic and insoluble, and his father worries about what will happen when he and his partner are no longer around. "It's a massive problem for everyone: for parents, for the children and for the caring services in decades to come. If the professionals don't work out what the rates are and what is causing autism, if rates continue to rise, the financial burden will be unimaginable - it could amount to billions."