Government plans to focus so heavily on mediation when couples separate will punish those with abusive or uncooperative partners, lawyers warned today.
Resolution, which represents 6,000 family lawyers and professionals, said mediation could be inappropriate in as many as two in five cases.
Justice minister Jonathan Djanogly has said the process of separation and decisions about future arrangements for children could be made simpler if families chose mediation.
But this would have been unsuitable in 5,416 of the 13,315 legal aid cases (41%) involving the association's members, Resolution said.
David Allison, the group's chairman, said: "The organisation welcomes the government's desire to see fewer family cases going through the court system.
"However, there needs to be support for those for whom mediation is inappropriate, which, according to the survey, could be in as many as 40% of cases.
"We are concerned that, by focusing so heavily on mediation, the government will punish those for whom it simply won't work through no fault of their own - for example, if they have an abusive or uncooperative partner."
Speaking as the £350 million-a-year cuts outlined in the government's Legal Aid, Sentencing and Punishment of Offenders Bill are expected to face fierce opposition in the Lords, he added: "It is clear that the government's proposed legal aid cuts could bring devastating consequences.
"The changes also risk increasing the nation's benefits bill. Many of our members say that the majority of their clients would not know what financial settlement they are entitled to, which could see them left dependent on the welfare state and benefits."
Under the planned reforms, 600,000 people will no longer receive legal aid, 68,000 children will be affected by the removal of legal aid in family cases, 54,000 fewer people will be represented in the family courts annually and 75% of existing private family law cases will no longer attract legal aid, campaigners have said.
Measures being introduced in the Bill would also see more people going to court on their own without legal representation, a move senior judges have warned could increase both costs and delays.
A Ministry of Justice spokeswoman said: "At more than £2 billion a year we have one of the most expensive legal aid systems in the world which has grown to encourage lengthy, acrimonious and sometimes unnecessary court proceedings at taxpayers' expense.
"We know that there are cases which are not suitable for mediation, particularly serious cases involving domestic violence, child abuse or child abduction and forced marriage, and we will ensure that legal aid will continue to be routinely available to those who need it most.
"However, it is not fair that the taxpayer should foot the bill when couples decide to part.
"If people are unable or unwilling to mediate they have the option to go to court but may have to pay to do so - and we have extended the powers for courts to require one party to pay towards the other's legal bills when they have the means to fund it."