Crown court barristers in England and Wales have given ministers a deadline to deal with their pay demands.
Barristers could refuse to take on new cases in protest
The Bar Council said a pay review was promised a year ago and must begin by 14 July or barristers would react with "anger and despair".
Hourly rates for the 95% of crown court trials which last up to 10 days have not changed since 1997, it argues.
A Department for Constitutional Affairs spokeswoman said it would "fulfil its commitments on this issue shortly".
Guy Mansfield QC, chairman of the Bar Council, has written to Lord Chancellor Lord Falconer saying any review should be completed by mid-September.
Mr Mansfield said: "The response of individual practitioners to the failure to produce a review will be anger and despair."
He said a pay scheme review should have started in May, but the council was told in June that there was no time set for one to start.
An overwhelming majority of barristers said they would take action if the government refused a review, according to a Criminal Bar Association survey conducted earlier this month.
Action could include refusing to take on new cases - the closest barristers could go to striking.
At the time, the government admitted pay was in need of reform but said overall the pay of defence barristers had risen.
The government's fixed pay rates known as "graduated fees" were introduced in 1997 and apply to crown court trials lasting up to 10 days.
Hourly pay rates for these cases do not include preparation time and expenses.
Current hourly rates for defending in legal aid cases are £33.50 for a junior, £47 for a leading junior and £62.50 for a QC.
Barristers want the rates to be kept in line with the rate of inflation at the very least.