Only one in five carers of people with autism have ever received the local authority assessment of their needs to which they are legally entitled, according to a major survey of carers’ needs.

Of more than 5,500 carers who filled in an online survey for the National Autistic Society (NAS), 80% said they had never been through the assessment process, which local authorities are obliged to provide and which helps them obtain the right assistance. Only 26% of those who responded said they received any help at all from a council or health authority.

More widely, campaign groups warn that poor information about support services coupled with spending cuts and wider economic worries have caused significant difficulties. “We call it a perfect storm for carers,” said Emily Holzhausen, policy director for Carers UK.

“Those juggling work and care feel more under pressure at work, benefits are under review and we also have rising charges and changes to services. The pressure is really loading up on families, and we see that through our helpline – we’re getting calls from very distressed people.”

The NAS figures, part of a wider study that also examined the problems faced by people with autism, found more than three-quarters of carers said they had been obliged to battle to receive support services.

The survey highlighted the extreme toll placed on those placed in such situations. More than 80% of the carers said the lack of support had caused them anxiety, with 64% saying it was a cause of depression. More than half said being a carer had directly affected their own mental health.

The study tallied with carers’ accounts given the NAS helpline and to individual branches, said Sarah Lambert, head of policy for the charity.

She said: “People say they are having to fight to get the help they need, and that has quite a significant effect on their own mental health and their relationships. Increasingly, with cuts to local services there will be gaps, for example fewer short breaks or respite services available, which can make that even more challenging.”

While it could be tempting for local authorities to view carer assessments as an expensive obligation, this was wrong, said Holzhausen.

“It might be easy for someone to say, this is another bureaucratic process – what does it add? It adds a huge amount. Not taking into account how the carer is doing is really a false economy. A lot of people really are pushed to breaking point, and then the cost to a local authority really rockets, for example if someone needs residential care.”

Carers’ groups are calling on the government to address the situation in the upcoming social care bill, one of those highlighted in this month’s Queen’s speech. They particularly want the bill to include recommendations from a three-year study into adult social care by the Law Commission, also published this month.

The commission report recommends that assessments also “focus on the carer’s ability to provide and to continue to provide care for the person cared for”, taking into account factors such as whether the carer can balance their duties with enough time for work, education and leisure.