A key disability benefit is not working for millions of disabled people or the government and needs fundamental change, a review has said.

Sir Stephen Timms told the BBC the interim review of Personal Independence Payments (Pip) in England and Wales had found it to be “not fit for purpose”.

People applying for the benefit said the process was “dehumanising” and a barrier to work.

The disability minister, who is leading the review, said his final report due out later this year was not expected to make “crude proposals” on payment changes.

But with the cost of Pip expected to rise to more than £41bn by 2030, the sustainability of this would “be a concern as we reach these decisions”, he said.

Speaking to the Today programme, Sir Stephen said: “My view is that the current level of spending is not a great concern. What would be a concern would be if it carried on going up forever more.”

Conservative shadow work and pensions secretary Helen Whately accused the government of being “in denial about the seriousness of the situation of our welfare system and the fact that we have to make savings”.

Last year, the UK government asked Sir Stephen to review whether Pip was “fair and fit for the future”. His initial report is being published on Thursday ahead of the final recommendations due in the autumn.

The interim report, published on Thursday,, external suggests a sweeping overhaul of the assessment system is needed.

It also highlights the steep increase in the number of Pip recipients in recent years and the forecast rise in spending on the benefit.

Pip is a benefit people with long-term illnesses and disabilities can claim if they need help with extra costs associated with living, work and care. Eligibility is determined through an assessment.

Under the current system, claimants are scored on a zero to 12 scale by a health professional on everyday tasks such as washing, getting dressed and preparing food.

Autism awareness campaigner Cheryl Fyfield said the Pip assessment process needed to change.

“It can be really hard to even qualify for Pip, let alone go through the process if you do qualify every three years,” she said.

“I’m autistic, I’m going to be autistic my whole life, yet every three years I have to go through the gruelling process to be reassessed.”

Sir Stephen told the BBC Pip “does a very important job in helping people meet the additional costs of disability”.

But he said disabled people had told the review the assessment can be “demeaning” and “deter you from participating in society”.

“We’ve also found that it hasn’t kept pace with changing understanding of health and disability over the last 13 years since the benefit was introduced, so we do think quite fundamental change is needed,” Sir Stephen said.

As of April there were about four million claimants entitled to Pip in England and Wales.

The number of Pip recipients has risen considerably since the benefit was introduced in 2013, with the increase fuelled by claimants citing mental health conditions in recent years.

Sir Stephen’s review commissioned by Sir Keir Starmer after his government’s attempt to reform welfare last year.

Dozens of Labour MPs expressed concerns about plans to cut disability and sickness-related benefits payments to save £5bn a year by 2030.

Fearing MPs would vote down the reforms, the government U-turned, saying it would not change Pip rules until it had time to consider the review’s conclusions.

By the autumn when the final report will be published Sir Keir’s successor will be in office, with Makerfield MP Andy Burnham widely expected to be prime minister.

Burnham told LBC last week he would not make “crude cuts to benefit levels that just put people who are struggling in even worse poverty”.

Sir Stephen said although he had not spoken to him yet about the review, he expected him to see this process through if he became PM.

“The final report will be delivered in the autumn, and I’m not expecting it to contain crude proposals,” Sir Stephen said.

“They’re going to be very well thought through proposals, thanks to this lengthy and very carefully considered exercise that we’ve gone through.”

But Sir Stephen said: “We’re certainly going to be looking fairly at how these decisions are being made, and the question of fiscal sustainability for the benefit is going to be a concern as we reach these decisions,” Sir Stephen said.

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