Sir Keir Starmer is facing mounting discontent as the government prepares to announce changes to the welfare system.

Work and Pensions Secretary Liz Kendall is to set out plans for reform on Tuesday in an effort to get more people back to work and cut the cost of spending on benefits.

Ministers have been looking at the eligibility criteria around Personal Independence Payments (PIP) – which are designed to help with extra living costs for those with long-term health conditions and disabilities.

It comes after Health Secretary Wes Streeting told the BBC’s Sunday with Laura Kuenssberg there was an “over diagnosis” of mental health conditions and too many people were being “written off”.

Speaking to BBC Radio 4’s Westminster Hour, the chief executive of Citizen’s Advice said the government was “pulling the quick and easy lever” by taking “money out of the system”.

Dame Clare Moriarty also accused the government of “not having done all the work to make sure that people can actually be supported into work”.

Asked what advice she would give to the work and pensions secretary, Dame Clare said: “If I was talking to Liz Kendall now, I’d be saying the way that they are going about this does not feel consistent with a government that really wants to raise living standards, tackle child poverty, end mass dependence on emergency food parcels.

“They really need to think about the consequences of taking this short term action.”

Several backbenchers have also expressed frustration at a lack of communication from ministers.

Speaking to the PA news agency, one Labour MP described “engagement sessions” held by No 10 as “a tick box exercise” and another said many colleagues had made it clear they would vote against such proposals.

Initial reports had suggested PIP would not rise in line with inflation for a year, but ministers are now considering abandoning those plans after many usually loyal Labour MPs voiced strong opposition.

After attending a private meeting of Labour MPs last week, one MP told the BBC that freezing PIP would be “unforgivable”.

“Some people have very complex disabilities. Part of the social contract is they are supported”, they said.

Another MP, a usual supporter of the prime minister, told the BBC: “Most of us broadly agree that there are lots of people who don’t work but should, and have no problem with getting them into work.

“But punishing those who are especially vulnerable and have severe disabilities is unacceptable.”

Writing in the Times on Monday, Labour’s Greater Manchester mayor Andy Burnham urged “caution” on benefit changes.

He said: “It would trap too many people in poverty. And to be clear: there is no case in any scenario for cutting the support available to disabled people who are unable to work.”

During his appearance on the BBC’s Sunday with Laura Kuenssberg programme, Streeting was asked if he agreed with experts that warn of an overdiagnosis of mental health conditions.

The health secretary said he wanted to “follow the evidence and I agree with that point about overdiagnosis”.

“Here’s the other thing, mental wellbeing, illness, it’s a spectrum and I think definitely there’s an overdiagnosis but there’s too many people being written off,” he said.

The health secretary’s comments prompted the mental health charity Mind to warn it was important to be “extremely careful” with the language around diagnoses to avoid stigmatising people.

Total spending on health and disability benefits is forecast to rise from £64.7bn in 2023-24 to £100.7bn in 2029-30.

The biggest contributor to this increase would be from welfare spending on working-age adults, according to the Office for Budget Responsibility.

PIP is the second-largest element of the working-age welfare bill, with spending on this projected to almost double to £34bn by 2029-30.

Shadow Education Secretary Laura Trott accused the government of being “all over the place and divided” over welfare reform.

When asked if the Conservatives would back the welfare changes, she said her party supported the “principle of welfare reform” but “we’re not clear on the plan”.

The SNP has urged Prime Minister Sir Keir Starmer to scrap the “cuts to disabled people”.

The party’s Westminster leader Stephen Flynn said the Labour government had “boxed itself in with its Tory austerity rules” on public spending.