The President of the New South Wales Bar Association, Phillip Boulten SC, says a proposal to water down a person's right to silence when they are arrested will not work.
The change is part of the State Government's response to bikie violence.
It means that a jury at a trial could draw negative inferences if a defendant refuses to answer police questions when they are arrested.
Mr Boulten says it will not work on uncooperative witnesses.
"The law will only operate if someone is already charged and has to face a trial," he said.
Mr Boulten says the new laws are based on the English system, where a lawyer is based at every police station giving free advice.
He says the New South Wales Government wants to provide a telephone hotline instead.
"The legal Aid Commission has made it clear they cannot afford to staff such a hotline," he said.
"It will be the English system without the safeguards and the English have found it to be extraordinarily expensive.
"They've found it to be extraordinarily complex, it raises a whole lot of very important issues that are fought out commonly in the courts."
Mr Boulten says a fundamental right is being stripped away for no real benefit.
A spokeswoman for the Attorney-General Greg Smith says the government has consulted widely and the changes will be announced shortly.