In a letter to the Daily Telegraph, 90 QCs condemn the proposals to restrict the judicial review process, claiming it will "seriously undermine the rule of law".
Among those who have signed the letter are Lord Goldsmith, the former Attorney General, Lord Macdonald of River Glaven, the former Director of Public Prosecutions, and Cherie Blair, who practices as a part-time judge under her maiden name Cherie Booth.
Justice Secretary Chris Grayling unveiled changes last month, aimed at dealing with the soaring number of applications for judicial reviews - court proceedings in which a judge reviews the legality of a decision or action made by a public body.
The Government will ban people from seeking a hearing in person if their initial written application has been ruled as totally without merit.
It will introduce a £215 court fee for anyone seeking a hearing in person after their initial written judicial review application has been turned down, and will also cut the time limit for applying for a judicial review of a planning decision from three months to six weeks.
"They are likely to drive conscientious and dedicated specialist public law practitioners and firms out of business. They will leave many of society's most vulnerable people without access to any specialist legal advice and representation." It went on to urge the Government to withdraw the proposals.
Announcing the changes, Mr Grayling said: ''Judicial review should be used by people who have carefully considered whether they have proper grounds to challenge a decision. We are changing the system so it cannot be used any more as a cheap delaying tactic.''
Judicial review applications rose from 6,692 in 2007 to 11,359 in 2011 - but just one in six were granted permission to proceed beyond the earliest stages, the Ministry of Justice said.
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