Two-thirds of people with autism feel they do not have enough support, according to a report backed by actor Richard Wilson.
The Merlin star spoke of a "palpable frustration" among those on the autism spectrum that their views are not being heard by organisations meant to help them.
He spoke out as figures revealed nine in 10 people with the condition want more say in what support they receive.
The report, by National Autistic Society (NAS) Scotland, will be delivered to SNP MSP Mark McDonald at Holyrood on Wednesday by the TV personality.
The publication's authors have produced a series of recommendations for bodies including the Government and councils, aimed at improving the lives of the 50,000 people with autism in Scotland.
NAS Scotland describes its report, entitled Count Us In: It pays to listen, as "a call to action for the Scottish Government to progress its strong commitment to people with autism and their families by giving them a say in the decisions that affect them".
A national survey which forms the basis of the report found 66% of people with autism feel they do not have enough support. Nine in 10 (91%) want a greater say over their support.
Seven in 10 adults with autism say they have not had their needs assessed since they turned 18. Four-fifths (79%) think that public understanding of their condition is poor or very poor.
Mr Wilson, who became an ambassador for the charity last year, said: "People with autism may see the world differently from many of us but they have strong, valuable opinions on the kind of support needed to access the same opportunities most of us take for granted.
"There is palpable frustration that those organisations meant to help are not listening to what they have to say."