Falling crime rates will deliver savings of more than £80 million a year on the Government's criminal legal aid bill without proposed cuts to the system, a study has claimed.
Ministers have assumed the crime case load will remain constant after the first year of cuts, a report from forecaster Oxford Economics said.
An alternative forecast to explore the impact falling crime could have on criminal legal aid spending should be considered, the report adds.
The fresh research, commissioned by the Law Society, the Criminal Law Solicitors Association and other legal groups, comes a week after barristers staged an unprecedented walkout in protest at
Ministry of Justice plans to slash legal aid budget by £220 million a year.
More than half of the savings - £120 million a year - are set to come from reducing fees paid for police station attendance, magistrates' court representation and crown court litigation.
But Oxford Economics said legal aid spending could be £84 million lower when allowing for a continuation of the steady decade-long downward trend in crime alone.
"The expenditure on criminal cases has not risen in two decades and is set to shrink further following more fee cuts. Additional cuts proposed in the latest plans could have a devastating impact on access to justice and many legal aid solicitors have already reached the point of despair.
"We are proposing a better way forward, so that our members may continue to uphold the rule of law and provide access to justice to the public. We will all be poorer if confidence in our criminal justice system falls."
The Ministry of Justice has previously said it is vital to scale back the legal aid scheme as it is the most expensive in the world.
The department has highlighted figures showing that 1,200 barristers judged to be working full-time on taxpayer-funded criminal work received £100,000 each in fee income last year.
Legal Aid minister Shailesh Vara said: "We believe the analysis on which the report is based leads to significant inaccuracies. If we had used this methodology in past years, we would have repeatedly overspent on our litigation legal aid budget."
However, the criminal bar has hit back as it revealed the same figures show the average barrister earns around £36,000.
Reforms also include limits on prisoners' access to legal aid, a household disposable income threshold for criminal legal aid and reductions in the cost of fees for representation.