Legal groups and opposition parties were furious at a U-turn by Holyrood's Justice Committee. It had been strongly critical of the proposals, under which those accused of crimes who have disposable incomes of £68 a week or more make a financial contribution to their defence bill.
Solicitors will be asked to collect contributions from clients in summary – non-jury – cases instead of receiving the entire fee from the Scottish Legal Aid Board if the Government's bill is passed.
As 200 lawyers protested outside the Scottish Parliament, SNP committee members backed the bill in a crucial stage-two vote on the plans.
The Edinburgh Bar Association said the move made strike action certain. Its president, Cameron Tait, accused the committee of "changing direction in line with political instruction and not taking the morally correct course of sticking to its guns". Austin Lafferty, president of the Law Society of Scotland, said: "It's great that so many chose to voice their concerns today. However, it is regrettable that the compelling arguments they and the society presented were not supported by a majority of the Justice Committee.
"The Scottish Government's latest drive to reduce the legal aid budget cannot be seen in isolation from the savings already made over the last few years. This has included significant cuts to the fees paid to solicitors for acting on behalf of people who cannot themselves afford legal representation.
"The profession has always tried to work constructively with Government in its bid to save money but the suggested collection proposal is simply unfair."
The Government insisted the plans would save almost £4m annually and affect fewer than 20% of prisoners.
The current impasse prompted senior police to claim potential action by lawyers could halt their interviews with suspects and make the system grind to a halt.
Critics have warned the moves will turn lawyers into unpaid debt collectors and raised fears some cases will be derailed if the accused cannot pay.
Mr Tait said Justice Secretary Kenny MacAskill's assurances meant little to the profession. He added: "We are disappointed that the party line seems to have been toed and we will clearly have to reflect on today's debate and decide where the profession goes from here.
"Strike action is clearly something the profession is considering and the outcome of today will certainly have a bearing on that.
"It's disappointing that the Justice Committee does, to an extent, seem to have changed direction in line with party instruction and has not taken the morally correct course of sticking to its guns."
Conservative MSP Margaret Mitchell moved a series of motions in line with Scottish Law Society objections to the proposals, saying the idea of making solicitors collect money "beggared belief".
Labour member Jenny Marra also tried and failed to persuade the committee to remove the contribution threshold from the text of the bill.
Mr MacAskill said: "I do not consider it unreasonable to expect a solicitor to collect his or her fee direct from the client who is being provided with legal assistance."