Ministers are being urged not to restrict legal aid for disabled people wanting to challenge benefit decisions.
A coalition of charities including Scope and Mind argues that limiting access to “vital” help in England and Wales would harm vulnerable people.
Labour says the plans due to be debated by MPs later are “unprincipled”.
But the government insists the £2bn legal aid bill is unaffordable and help has to be targeted at the most serious cases and those most needing support.
Ministers are looking to prune £350m from the civil legal aid budget by 2014-5 as part of cuts across government to reduce its deficit.
Justice Secretary Ken Clarke has argued that the legal aid bill has spiralled in recent years and, with resources being squeezed across Whitehall, only cases where life or liberty are at stake should be routinely funded out of the public purse.
It is thought there will be 500,000 fewer civil cases as a result.
The 23 organisations, which also include Mencap, the RNIB and Leonard Cheshire, want MPs to back an amendment to the Legal Aid and Sentencing Bill – put forward by Lib Dem Tom Brake – reversing the decision when the proposed legislation is debated.
The disability rights groups say the changes mean up to 80,000 people will no longer be able to get access to publicly funded legal advice to help them challenge benefit decisions.
Campaigners say those affected will not be able to find legal help elsewhere and it could have a “serious impact” on their finances and peace of mind – making it harder for them to return to work in the future.
Cutting legal aid in this area will make it harder for disabled people to get the right support and ultimately could drive more people further away from work”
Richard HawkesChief executive, Scope
“Legal advice is vital for disabled people if they fall foul of poor decision-making, red tape or administrative error,” Scope’s chief executive Richard Hawkes said.
“For welfare reform to work, disabled people have to get support to appeal decisions relating to their benefits, especially within a system where errors are commonplace.
“Cutting legal aid in this area will make it harder for disabled people to get the right support and ultimately could drive more people further away from work.”
Citizens Advice has warned the plans could be counter-productive since the £16m in anticipated savings will be exceeded in the long-term by the costs to the state as peoples’ problems “spiral out of control”.
The Ministry of Justice said the move was necessary as part of plans to scale back the legal aid bill.
“We have one of the most expensive legal aid systems in the world which in the current financial climate we just cannot continue to afford,” a spokeswoman said.
The review of legal aid, she added, would ensure it was “targeted at the most serious cases and those who most need legal support”.
“Legal Aid will continue to be available in many types of cases including where someone is at risk of serious violence, losing their liberty or their home, or where children may be taken into care as well as for mental health, community care work, and child abduction.”
But Labour said the proposals would limit access to justice to those who could afford it.
“Receiving legal advice to prevent escalating housing, welfare and debt problems has been shown to save the taxpayer money further down the line, demonstrating just how economically unsound as well as unprincipled the plans are,” shadow justice secretary Sadiq Khan said.
“Savings must be made to bring the legal aid budget down but it should be through other areas such as retendering criminal law contracts, not by restricting access to legal aid for those in greatest need.”
Following a public consultation earlier this year, Mr Clarke amended the plans so as to protect access to legal aid for victims of domestic violence in private family cases and for children at risk of abuse or abduction.