Young people whose complex disabilities mean they have little prospect of getting a paid job should get fast-track access to disability benefits, an official review of youth employment will say.

The review, by the former Labour health secretary Alan Milburn, will say 16- to 24-year-olds with the most severe lifelong needs should be guaranteed swift and unconditional benefit support rather than having to prove they cannot work.

Currently, many disabled youngsters and their families have to endure repeated lengthy, adversarial and often distressing assessments to access personal independence payment (Pip) and universal credit health benefits.

The guarantee could include young people with profound and multiple learning disabilities, severe neurological conditions, and those with severe and complex needs who qualify for NHS continuing healthcare support.

The review, expected in October, will say there is no need for repeated disability benefits assessments for this group, and young adults should not have to constantly demonstrate proof of lifelong conditions and impairments diagnosed at birth or in early childhood that mean they cannot work.

"I've heard too many stories of young people with the most severe disabilities left waiting, worrying and fighting for the support they're entitled to," Milburn told the Guardian. "Too often they're having to battle through dehumanising tick-box assessments designed to catch people out, not care for them."

He added: "A different approach is needed for disabled people whose condition is so severe that they could never work. By right they should get faster support rather than having to prove it over and over again to get the help they deserve."

The separate government-commissioned Timms review into Pip concluded in an interim report earlier this year that the Pip assessment process was justifiably regarded by many claimants as "soul-destroying" and degrading.

The disability charity Sense, which supports disabled people with complex needs, welcomed the principle of fast-track guarantees but said it was important young people who were able and willing to work were not written off.

Harriet Edwards, the director of influencing at Sense, said: "It would be a significant step forward for young disabled people with the most complex needs and their families, and for those who have long campaigned to end the exhausting and humiliating process of multiple assessments.

"But we must not write young disabled people off. Those who want to and are able to work need specialist employment support and genuine opportunities, alongside the financial protection they need to live their lives.

"Government must now take this recommendation forward. The detail will be crucial, including who is eligible, whether exemptions go far enough, and how this will work across different disability benefits so people aren't left navigating different rules and assessments."

Tara Harris, 57, from the West Midlands, described obtaining disability benefits for her son Ollie, 25, who has complex disabilities, as a "bureaucratic nightmare". She said the system involved "constant battles of chasing things and not having things. It's 'computer says no.'" It was also stressful. "I feel like I've had to be a tiger mum," she said.

Harris said her son could not do paid work but had been supported to volunteer at a cafe two days a week. The Pip assessment required her to describe his progress in a routinely negative way. She fears that if she were to "put things in a positive language, then you don't get Pip".

She said: "It's really hard to have these sorts of conversations in front of Oliver. Because it sort of demeans him, and he's absolutely wonderful, amazing person and deserves to have money to be able to be an adult."

The government commissioned Milburn to address a growing youth jobs crisis in the UK in which nearly 1 million 16- to 24-year-olds are classified as Neet (not in employment, education or training).

His interim report, published in June, made it clear young people diagnosed with lifelong complex needs who are never be able to work must be protected by the benefit system. But it also hinted that young people with less severe conditions who could be supported to work may see reductions in benefits

Milburn, a minister in Tony Blair's government, last month called for investment in specialist internships designed to secure work for young people with special educational needs to address "devastating" joblessness rates for those with learning disability, autism and mental illness.