Peers have warned the government is failing to deal with a miscarriage of justice akin to the Post Office scandal, after ministers refused to back legislation that would give new sentences to thousands of prisoners jailed indefinitely.

James Timpson, the prisons minister, said the 2,964 people currently serving indeterminate sentences would in future have a better chance of being released, with more regular reviews of their readiness every six months.

Releasing a report on imprisonment for public protection (IPP), he said there would be a new traffic light system that would rate the prisoners green, amber or red in terms of their progress towards being released.

However, Timpson refused calls from peers to embark on resentencing of the prisoners, saying it would put the public at “an unacceptable risk of harm”.

IPP sentences were given to offenders convicted of serious violent or sexual offences where a judge believed they posed a significant threat to the public but did not merit a life sentence. They were abolished in 2012 for new offenders but this did not apply retrospectively.

Since then, campaigners and families of the prisoners have sought to highlight many prisoners on indeterminate sentences who committed only minor crimes. The prisoners have had a high rate of suicide and mental health problems that has made it harder for them to make the case for their release.

The government’s new report showed that 86 prisoners on indeterminate sentences have committed suicide – including a record nine in 2023 alone.

Labour peer Tony Woodley, who has brought forward the imprisonment for public protection (re-sentencing) bill without government support, told the House of Lords the current IPP regime was a miscarriage of justice and lords should not wait for an “ITV docudrama” to portray them as “uncaring, cold-hearted time wasters who left damaged people … to rot away in prison”.

The government brought in changes this month that mean some IPP offenders now on licence have had their sentences ended earlier. The reforms mean licence conditions for 1,800 IPP offenders who were released from prison at least five years ago, but have not been sent back to jail within the last two years, will end immediately.

However, the Lords heard that 1,095 prisoners are on IPP sentences and have never been released from prison, while two-thirds have served more than 10 years beyond their initial sentence. Almost 1,600 have been recalled to prison after initially serving on an IPP. About 269 have been released from prison but are still serving IPP sentences.

Lord Woodley said: “Many prisoners are still living this nightmare and it’s those people who I focus my bill on, which quite simply seeks to convert these never-ended IPP torture sentences into regular, normal, determinate sentences with an end date, giving them hope.”

Crossbench peer Michael Hastings told peers about an ex-prisoner, Mike, who had been on an IPP sentence and was recalled to prison and served a further 10 months after forgetting to tell his probation officer he was going on holiday with his wife – 17 years after being released.

“What a waste of public money, what a scandalous destruction of a marriage opportunity,” he said. “What a pernicious persecution of an individual’s freedom, hard-earned, for a simple act many decades earlier.”

Conservative peer Edward Garnier, who held ministerial positions in the Ministry of Justice as an MP, said: “The English language is a rich one but even it runs short of adjectives to describe the disgusting state of affairs that is described by people being recalled to prison for an indefinite period for minor breaches of their licences.”

He urged the government to support the bill, adding: “Saying it’s all too difficult and we can improve things only at a risk-averse glacial pace is unacceptable, inhumane and uncivilised.”

Sarah Ludford, a Lib Dem peer, said: “I ask how many scandals have to be endured by the citizens of this country before a government finally say, “No, we are not going to repeat the mistakes of the Post Office Horizon scandal or Windrush or infected blood or Hillsborough or Grenfell. We are going to act to right wrongs and address horrendous injustices”.

However, David Wolfson, the Conservative justice spokesperson in the Lords, said the current bill would not have Conservative support as it would mean the automatic release of dangerous prisoners.

He said: “Those still in prison and who have never been released on licence were sentenced over 12 years ago. During that time, they will have been prepared for and attended several Parole Board hearings and the Parole Board, which is independent and expert, will have concluded on all the material before them that it was not safe to release them.”

Timpson said: “Legislating to give every IPP prisoner a definite release date and post-release licence, or legislating to provide for a resentencing by court, would result in them being released automatically.

“This would be the case even where the Parole Board had previously determined, and in many cases repeatedly, that they continue to be too dangerous to be released and they have failed to meet the statutory release test. Either legislative approach would put the public at an unacceptable risk of harm, which the government is not prepared to countenance.”

He added: “With continued support, all IPP prisoners for whom it is safe and appropriate can and will be released.”

A Ministry of Justice spokesperson said: “It is right that IPP sentences were abolished, and we recently terminated the licences of 1,742 rehabilitated offenders.

“This government is determined to do all we can to support the remaining IPP prisoners – with new tailored plans for those struggling to progress. This includes urgently ensuring all IPP prisoners are in the best prison to access the rehabilitation support they need.”