The Prime Minister has faced pressure over the controversial scheme during his first few days in No10
Andy Burnham has freezed the early prison release scheme following fury over PC Andrew Harper's killers potentially walking free.
Labour has been battered with criticism after entertaining the plan to allow offenders back onto Britain's streets.
Prison chiefs have now been ordered to halt the rollout of the plans, The Times reported.
The Prime Minister promised to review the programme after it was revealed the murderers of PC Harper could be released under the legislation.
Earlier today, the police officer's widow, Lissie, said it was "deplorable" her husband's killers could be allowed to roam free under Labour's attempt to tackle overcrowding in prisons.
She accused Labour of betrayal after cross-party support assisted the creation of Harper's Law, which introduced mandatory life sentences for those who kill emergency workers while they commit crime.
Mrs Harper insisted her plea was "not about politics" but more about asking if "justice is something we truly believe in, or something that can be negotiated away when it becomes inconvenient".
PC Harper was just 28 years old when he sustained fatal injuries while responding to a quad bike theft in Sulhamstead, Berkshire, in August 2019.
He died after getting caught in a strap attached to the back of a car and dragged down a country road as three teenage suspects fled the scene of the burglary.
His killers were handed 13 years in custody for manslaughter after a trial at the Old Bailey in 2020.
After furious retaliation over the killers' early release, Mr Burnham said that he would review the plan.
The new Prime Minister said: "We did not invest in the prison estate when we should as a country, going back a decade or so ago when it was clear that there was going to be pressure. That has created an unacceptable situation now.
"But I want to assure myself that everything has been looked at before this policy proceeds and I can give that assurance that, every single part of this, I will look into with the justice secretary.
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"I can’t say that I can change the policy completely but I will look at it in detail before we go further forward."
Now, a deputy governor of a prison said that they have been instructed to "put planning on hold until it's clear what the new ministerial teams' intensions are", The Times revealed.
The Sentencing Act 2026 introduced under Sir Keir's top team would create an "earned progression model" allowing prisoners out of jail early based on behavioural assessment.
Most would be allowed back onto Britain's streets only having served a mere third of their sentence, rather than 50 per cent.
The remainder of their sentence would be overseen by "strict supervision" with e-tagging.
Meanwhile, sex offenders will be allowed to roam free will now be allowed out having served half the prison term, as long as they have not breached prison rules.
The same applies to violent criminals, such as Albert Bowers and Jessie Cole, who killed PC Harper.
Mr Burnham has provided assurances that Henry Long, who was the main perpetrator, "will not be subject to any release".
