George Osborne risks another parliamentary defeat only a week after the government lost a vote over plans to liberalise Sunday trading laws.
Plans to change payments to disabled people face a growing backlash from some Conservative MPs, including a number of Christians.
David Burrowes, the MP for Enfield Southgate who led the Tory rebellion on Sunday trading, told Christian Today the government needs to "rethink its plan".
"Conservatives have a good record in supporting the disabled which is at risk if we press ahead with this unfair cut to PIP," he said.
He told Christian Today the measure was a "quick fix to the gap in public finances" and urged the government to spend more time on "long term reform on disability benefits".
The changes would cut the Personal Independence Payment (PIP) for disabled people by £1.3 billion over the next five years. The Office for Budget Responsibility estimated 370,000 people would lose an average of £3,500 a year. The payment reduction would particularly affect those who need aides help to dress and go to the toilet.
Burrowes was at pains to praise the government's welfare reforms and economic strategy in an article for the Guardian but said he was "yet to be convinced" about the proposed cuts.
"It is hard to maintain the claim of fairness when 'aids and appliances' to help disabled people go to the toilet and get up in the morning are to be downgraded while, for example, comparatively wealthy individuals are to receive a cut in capital gains tax."
Burrowes joins a chorus of Conservative MPs who have expressed concern about the measures.
Andrew Percy, Conservative MP for Brigg and Goole said the government was hitting "exactly the wrong people" with cuts and Johnny Mercer, Conservative MP for Plymouth Moor View also tweeted his opposition.
Last day in Washington. Trying to get detail on the budget yesterday. Concerned by proposed changes to PIP. Not sure right direction.— Johnny Mercer MP (@JohnnyMercerMP) March 17, 2016
We must look after our most vulnerable at every turn. No doubt welfare spend still too high, but for those who really need it,it is lifeline— Johnny Mercer MP (@JohnnyMercerMP) March 17, 2016
The level of anger was made clear after Zac Goldsmith, the Conservative candidate for mayor of London, was asked to step down as patron of his local Richmond AID disability charity. Kit Malthouse was also told to resign as patron of MS Society and James Cleverly as patron of Advocacy for All.
Nicky Morgan, the education secretary who is also a Christian, raised hopes of a government climbdown after she said on BBC Question Time the plans were a "suggestion" and "under consultation".
However on Friday morning a source close to work and pensions secretary Iain Duncan Smith said her remarks don't "tally with what we and Downing Street are saying", according to the BBC.
Morgan didn't "seem to understand" the proposals, said the source.
A number of Christian charities wrote to the minister for disabled people and urged him to change the plans. The letter, seen by Christian Today, warned "damage the health and wellbeing" of up to 600,000 people.
Founder of Compassionate Britain Tanya Marlow, one of the signatories, told Christian Today: "In 2010, David Cameron promised compassion, and yet he keeps targeting cuts at the most vulnerable in our society.
"Government cuts have already affected disabled people nine times more than the average person and severely disabled people 19 times more. Now they want to introduce a back-door cut to a vital disability benefit."