Liberty, the Medical Foundation for the Care of Victims of Torture and Asylum Aid have joined with more than 40 organisations in a coalition to oppose government plans to cap legal aid to asylum seekers.
The Department for Constitutional Affairs wants to impose a limit of five hours on the amount of publicly-funded legal advice available to asylum seekers and immigration applicants.
In his speech to his party conference earlier this month, Prime Minister Tony Blair promised to "derail the gravy train of legal aid".
But the coalition argues that the plans will deny people the right to adequate legal representation and inadvertently boost costs by generating endless appeals to the courts.
Mark Littlewood, director of campaigns at Liberty, said: "There are civil liberties groups, community groups at the coal face and the legal profession in this coalition. We aim to demonstrate that the Government is standing alone, or maybe alongside the Daily Mail, in trying to push this through. It is a recipe for disaster."
The campaign will highlight "six-hour cases" - people who won the right to settle in the UK, but whose cases would have failed had the five-hour limit been in place.