Standing in front of a coffin marked: "RIP legal aid," hundreds of lawyers ? many in wigs and gowns ? demonstrated outside parliament on Wednesday.
The protesters oppose government plans to cut £220m from the annual budget for criminal legal aid and remove defendants' rights to choose their solicitor.
Sadiq Khan, a former solicitor and Labour's justice spokesman, accused the justice secretary, Chris Grayling, of destroying legal aid.
He said Grayling's "obsession with throwing red meat to Tory backbenchers and appearing on the front page of the Mail on Sunday" would undermine British justice.
Among others supporting the protest were the Blur drummer David Rowntree, Lady Kennedy, the legal campaigner Clive Stafford-Smith and Gerry Conlon, who was one of the Guildford Four. As many as 500solicitors and barristers took part in the protest.
Opponents of Grayling's proposals say that cutting legal aid will lead to more miscarriages of justice.
Kennedy said the reforms would result in the "Americanisation" of the system.
"This plan is about creating public defenders who will be chosen by the state to represent you," she said. "This is disgraceful. How much money is being spent from the public purse on defending this government? How much money was Jonathan Sumption QC paid to represent Tony Blair at the Hutton inquiry? These changes will mean many more miscarriages of justice."
Jonathan Cooper QC said people did not realise they needed legal aid until they become involved in a case. "Everyone understands that they may need the NHS at some point but people don't believe they may need legal aid."
The former Conservative MP Jerry Hayes condemned Grayling's statement that those arrested were too poorly informed to choose their criminal defence lawyer. He said the justice secretary was implying they were "too thick to pick".
"Independent lawyers will disappear within two years. High street solicitors will close down and the British justice system will be handed over to corporate bloodsuckers," Hayes said.
Many of the placards referred to the legal subsidiary of the haulage firm Eddie Stobart, the only firm that has expressed an interest in the proposed legal contracts.
"Truck Off Stobart," declared several placards. Lawyers wore T-shirts declaring: "Truck off Grayling, Save UK justice."