Probation workers have said the service is 'in chaos' following the government's decision to privatise parts of the system.
Speaking at a Labour party conference fringe event, NAPO spokeswoman Tania Bassett said the performance of the probation service since moving into private sector hands was worse than the union first feared.
Bassett said staff morale is lower than ever, with large numbers of probation workers leaving the service altogether.
The government has introduced contracts on a payment-by-results basis for around 70% of the probation service.
Bassett said probation workers assigned to different companies cannot talk to each other or even share stationery.
Some are working on 70 high-risk offenders at any one time, while 2,000 cases are still unallocated with no supervision or monitoring. Bassett also noted that IT breakdowns had meant that workers could not access important court or prison records.
'The government is in complete denial - these are not teething problems, they are having a direct impact on people's lives,' she said.
'This summer two members took their own lives - one chose to write her own eulogy in which she talked about the changes.
'It is putting the public at harm and causing delays in courts and prisons, putting immense pressure on our members who are leaving in droves.'
Bassett called for an independent inquiry to judge the success of the privatisation programme and its impact on the justice system.
Shadow justice secretary Sadiq Khan, also appearing at the event, said the changes had been 'rubbish', although he warned it would be expensive to tear up contracts if the government commits to 10-year deals with expensive break clauses inserted.
Khan also proposed the law should be changed so that private companies running public services should be subject to freedom of information requests.