Fewer than one in six people with autism are in full-time employment and a third live without a job or benefits, the National Autistic Society says.
In a report, the charity accuses the Government of condemning people with autism to a life of poverty.
Many people with the condition are forced to rely on family and friends for support, often for years. There are 300,000 adults of working age with autism in Britain. Although they are keen to work, they are being held back by a lack of understanding of the condition among employers and a dearth of specialist employment advisers.
Mark Lever, the chief executive of the society, said: “It is absolutely vital they are able to access the right help and services if seeking employment and are supported financially when they cannot work. It is scandalous, therefore, that thousands of people with this serious, lifelong and disabling condition are being consigned to poverty by a complex and counter-productive benefits system. We will keep campaigning until the Government’s “no-one written off” pledge is a reality for people with autism.”