Legal aid practitioners are claiming thousands of people could be deprived of legal advice if the Government goes ahead with new proposals to remove criminal advice from the Green Form scheme.
The Lord Chancellor's Department has written to the Law Society asking for its comments on the proposed change, which has taken practitioners by surprise.
Last year there were 377,564 acts of criminal Green Form assistance costing £23.6m.
The LCD argues that "at present the police station and magistrates court duty solicitor schemes are available to deal with urgent matters, and full criminal legal aid is available for the normal criminal process where the interests of justice require it".
Under the current arrangements solicitors can offer free advice and assistance to clients on income support or very small incomes, knowing they will be paid by the Legal Aid Board at a fixed hourly rate.
David Hartley, a professional policy executive at the Law Society, said it wanted to make sure people who needed advice on criminal matters outside a police station could get it.
"At the moment our view is that the Green Form scheme is a cost-effective and efficient way of delivering advice," he said. "We are surprised that it has been chosen for detailed consideration for change."
Bill Montague, co-chair of the Legal Aid Practitioners Group, said the principle of free advice and assistance should be upheld in any civilised democracy.
He said under the Green Form scheme people could get advice and assistance before they got into trouble and were in court or a police station. He added: "It is in the interests of society as a whole that they get it at the right time to avoid further costs to the taxpayer."
Franklin Sinclair, vice-chair of the Criminal Law Solicitors Association, said the plan would "cause criminal lawyers great uncertainty over whether they are going to get paid for giving advice and assistance to people who cannot afford to pay for it".
He predicted that "thousands of poor people will not be able to get advice" and said that if the proposal was introduced there would have to be "substantial exceptions".