More than 70 charities have urged ministers to axe planned disability benefit cuts ahead of a parliamentary debate in which Tory MPs are backing calls for a postponement.
The Disability Benefits Consortium (DBC), which includes Age UK, Sense, Mind and Sue Ryder, has sent an open letter to Work and Pensions Secretary Damian Green arguing against reductions to Employment and Support Allowance (ESA) and universal credit.
ESA payments are due to be cut by £29 a week to £73 from April for new claimants in the work-related activity group (Wrag) - those unable to work at present but judged capable of preparing to return to work, by attending interviews and training.
Cuts to universal credit will reduce the amount people are able to earn before their benefits are withdrawn.
Labour used a parliamentary debate on Wednesday to warn the reductions amount to around £4.8 billion, with Tory former work and pensions secretary Iain Duncan Smith among those urging the Government to scrap the proposed cuts.
A cross-party group of MPs is now backing a non-binding backbench motion - to be put before the Commons on Thursday - which includes Conservatives Jeremy Lefroy (Stafford) and Heidi Allen (South Cambridgeshire).
The motion suggests the Government should use next week's Autumn Statement to "postpone the cuts" to ESA and universal credit until "appropriate alternative measures to progress the commitment to halve the disability employment gap" have been considered.
They also want this action to ensure current and future claimants receive support so "sick and disabled people are supported adequately when they are unable to work".
Outside the Commons, the DBC letter has been signed by 74 charities and notes "deep unease" among MPs of all parties has been caused by the proposals.
It adds to Mr Green: "The Government promised further support would be given to disabled people in the Wrag to find work, however the recent green paper offers little detail as to where this would come from or how it will mitigate the effects of the cut.
"Almost 70% of sick and disabled people we surveyed say this cut would cause their health to suffer and just under half said they would probably not be able to return to work as quickly.
"We urge MPs from all parties to act - at a time when one in three households with a disabled member are living in poverty - and halt this cut immediately."
The DBC said its survey involved more than 500 people and took place between August 3 and October 15.
Speaking during Wednesday's debate in the Commons, Work and Pensions Minister Damian Hinds insisted real terms spending on disability benefits by the Government will be higher by 2020 than it was in 2010.
He also said there will be "no cash losers" among those claimants already receiving ESA or its universal credit equivalent.
In his speech to MPs, Mr Hinds added: "We believe that the change in the work-related activity group, working in tandem with the new employment support package announced in the green paper, will help to provide the right incentives and support to assist new claimants who have limited capability for work."