The government yesterday announced a 50% increase in spending on research into autism, which is thought to affect 520,000 people in Britain, but continued to insist there was no evidence of a link to the three-in-one measles, mumps and rubella vaccine.

The extra £2.5m for a programme led by the medical research council came as ministers prepared to step up their £3m campaign to encourage parents to inoculate children with the multiple jab, after one researcher, Andrew Wakefield, raised questions at possible links with bowel disorders and autism.

Some funds are likely to be used to investigate the significance of bowel disorders in autistic children, although not specifically a link with the MMR vaccine.

Critics have recently accused the government of being more interested in bullying parents than finding out the causes of autism. The Department of Health informed the research council of the new funding on Wednesday, but it is also considering putting extra money into the MMR publicity drive, which has involved television slots and information for GPs.

The government last year asked the research council to assess the state of knowledge about autism, a lifelong developmental disability. The council accepted it was less rare than previously thought, but concluded that the apparent increase was likely to have resulted from better diagnosis, clearer definition of disorders related to the condition, and increased awareness.

It said there was a need for further research on environmental factors, such as diet, drugs, toxins and infections, and their interplay with people's genes.

Judith Barnard, of the National Autistic Society, welcomed the funding, but said it should be ringfenced for years to come. "Autistic spectrum disorders are strongly genetic, but not wholly so. This means environmental factors are also involved, but these remain a mystery. Urgent research is needed."