Children with learning disabilities are being let down by society, according to a report by a leading health inequality expert.
Prof Sir Michael Marmot said they die 15-20 years earlier than other people due to poor housing, low incomes, social isolation and bullying.
He said 40% of people with learning difficulties were not diagnosed in childhood - and this had to change.
Learning disabilities affect 2.9% of the population.
But a quarter of young people in custody have learning disabilities, the report said.
Prof Marmot, from the Institute of Health Equity at University College London, estimates that shorter life expectancy affects 1,200 children and adults in this vulnerable group, who are also at higher risk of mental illness.
He said more should be done to improve the lives of all children with learning disabilities.
"We can make sure the voyage through education is as good as it can be, we can make sure people are not falling below the poverty line and we can educate the general population so that there is less discrimination against people with learning disabilities," he said.
And he said it was everyone's responsibility in society to take action.
"I want the society of which I am a part to do the right thing for the most vulnerable members."
Prof Marmot published a review of health inequalities in 2010, which recommended policies to allow a child to maximise his or her opportunity to lead as long and healthy a life as possible.
But he said 18-year-olds with learning disabilities today may not living long enough to draw their pension.
He said action should focus on:
- improving support to parents
- reducing poverty and improving living environments
- increasing work programmes for people with learning disabilities
- improving social integration and reducing bullying