The criminal justice system in NSW needs a major overhaul to tackle the growing backlog of cases and improve the efficiency of the courts, a former Supreme Court judge and law reform commissioner has urged.

The District Court, which hears the bulk of serious criminal cases across the state, is at breaking point with almost 2000 trials pending and a shortage of judges to hear the matters.

The NSW Law Reform Commission has warned the system is "in, or approaching, a state of crisis" and major systemic reforms are required.

"It's not meant to be alarmist," said former Supreme Court judge Anthony Whealy​, QC, the lead law reform commissioner behind its latest report. "It's meant to be a cold, hard appraisal of the situation."

Figures released on Monday by the Bureau of Crime Statistics and Research show a sharp increase in the time taken to finalise criminal trials. It now takes an average of 300 days to finalise a case against an accused person who is being held in custody, up 44 per cent from 209 days in 2007.