Shadow justice secretary Sadiq Khan criticised Chris Grayling's plans for privately-contracted probation services:
Payment by results in criminal justice is untested, and the Tory-led Government are taking a reckless gamble with public safety.
Pilots were already under way to see if payment by results worked and to ensure any problems were ironed out before being rolled out.
The new Justice Secretary, Chris Grayling, is demonstrating breathtaking arrogance in choosing to ignore the pilots.
Mr Khan said that every Probation Trust in the country was rated either good or exceptional by the Government in 2011, and warned that Mr Grayling's proposals risked replacing them with private firms such as G4S.
Rushing into payment by results is a danger to the offenders who might not receive the rehabilitation support they require, and to the safety of communities up and down the country.
And the Work Programme is showing that experienced and dedicated small and local providers won't be doing the delivery, but will be crowded out by the usual large private sector companies.
Probation reform proposals unveiled today by the Justice Secretary include plans for private contractors to provide services under "payment by results" deals.
Chris Grayling said: "We know across the public, private and voluntary sectors there is a wealth of expertise and experience - we need to unlock that so we can finally begin to bring down our stubbornly high reoffending rates.
"Our proposals will see all of those sentenced to prison or probation properly punished while being helped to turn away from crime for good. They will also mean we only spend taxpayers' money on what works when it comes to cutting crime."
The reforms will see the public sector probation service continue to deal with the most high risk offenders, including all serious sexual and violent offenders.