Hundreds of lawyers are due to demonstrate outside Parliament in a "desperate attempt to save Legal Aid and access to justice".
The unprecedented action has been sparked by the mismanagement of Legal Aid lawyers by the Legal Services Commission (LSC) and the Department for Constitutional Affairs (DCA), organisers said.
Legal Aid lawyers claim their action has been sparked by a disregard for the facts by both organisations, unwillingness to listen and determination to impose measures which will irreparably harm the system.
They claim it will result in a loss of access to justice to the most vulnerable people in society.
Roger Peach, chairman of the Criminal Defence Solicitors Union, said: "The Government intends to drive hundreds of Legal Aid firms out of business.
"This monopoly purchaser is performing an experiment without precedent in contracting a public service, which will create advice deserts and leave tens of thousands of people unable to access justice."
Greg Powell, president of the London Criminal Courts Solicitors Association, added: "If there is any part of Government unfit for purpose, it is the Legal Services Commission.
"They have lost the confidence and trust of Legal Aid suppliers as well as their grip on reality."
Demonstrators said the cost to the public purse of Legal Aid is "tiny" - less than half a per cent of Government expenditure.
Organisers said the system is being put at huge risk and after 10 years of price freeze, Legal Aid rates have lost 23% of their value.
