An overhaul of the probation service in England and Wales will see low risk offenders supervised by the private sector, the government is to announce.
Justice Secretary Chris Grayling will unveil plans to let security firms and voluntary groups manage probation on a "payment by results" basis.
Prisoners serving short sentences will also have to undertake compulsory rehabilitation for the first time.
The probation union has warned the move could "compromise public protection".
'Rehabilitation revolution'
Most released prisoners and people serving community sentences are currently managed by the public sector probation service - provided by 35 probation trusts across England and Wales.
But under the Ministry of Justice's proposals - which are subject to a six-week consultation period - responsibility for monitoring some 200,000 medium and low risk offenders will be transferred from 35 local trusts to the private sector.
Private companies and charitable bodies successfully bidding for probation contracts will be paid according to the results they achieve in cutting re-offending.
However, the public probation service will continue to supervise some 50,000 high-risk offenders, including all serious violent and sexual offenders.