Senior probation officers have criticised Government's plans to involve private and charity groups in the supervision of offenders.
The changes, announced by Justice secretary Chris Grayling, would see the private and voluntary sector being paid according to results in an attempt to reduce re-offending.
Under the plans, all offenders sent to prison would undergo a 12-month period of compulsory supervision after they have been released.
Sarah Billiald, from the Probation Chiefs Association, accused Mr Grayling of "dismantling" a "high performing system" on BBC Radio 4's Today programme.
"Our message is to ask really, why, when you have such a high performing service... it has met all its targets... why would you not build on that success rather than dismantling it later?"Labour claimed that the government have "failed to deliver" on prisoner rehabilitation and are pursuing "untried and untested" plans.
Justice secretary Chris Grayling said the reforms represented a "golden opportunity" to tackle high re-offending rates that has "dogged successive governments for decades".
Mr Grayling said: "These reforms are essential and will ensure that offenders are properly punished but also given targeted support to help them turn away from crime for good."
Re-offending rates have failed to decrease for more than a decade with more than 58% of prisoners who have served sentences under 12 months, committing further crime within a year of release.
A former prisoner and drug addict told ITV News that it is "absolutely imperative" that offenders receive support when they leave prison.
The new supervision will also help rehabilitate offenders with support in housing, employment, training and substance abuse.
The government plan to create a network of around 70 "resettlement prisons" where offenders will be released into making it harder for offenders to move homes while they are under supervision.
Under the plans, England and Wales will be divided into 21 areas, which will align with local authorities and Police and Crime Commissioner areas.
It is estimated that 65,000 new short-sentence prisoners will be subject to the new 12-month supervision and receive extended rehabilitation.
Shadow justice secretary Sadiq Khan said the government would be taking "big risks" with public safety and taxpayers money by implementing these policies.
He said: "This is another wasted chance by the Government - it should have pursued a model that focused on evidence of what works to reduce re-offending.
"Instead it has obsessively pursued pet projects leading to the imposition of an untried and untested payment by results model on the probation service which will take big risks with public safety and taxpayers' money."