The mother of an inmate, who is still in prison 18 years after receiving a “cruel and unfair” indeterminate prison sentence, is calling on MPs to back a bill to sentence all 2,734 inmates in her situation, who is still behind bars.

James Lawrence, 37, from Southampton, was given a prison sentence for public protection (PPI) in 2006 for threatening someone with a fake gun.

His mother, Mandy Lawrence, said: “My son has seen killers come in and killers go home again and he is not a murderer. It’s ridiculous.”

The Ministry of Justice rejected the idea of ​​resentment in the interest of “public protection”.

Although IPP sentences have since been abolished and Lawrence’s minimum term was just eight months, he has no idea when or if he will be paroled.

“He feels desperate, I know that,” his mother said as she described what led to him being sent to prison when he was 19.

Lawrence pleaded guilty to two felonies – one count of assault and one count of possessing an imitation weapon with intent to cause fear and violence.

Miss Lawrence said he suffers from post-traumatic stress disorder (PTSD) after he was almost stabbed to death in Southampton a year earlier.

She explained: “It was in 2005 when he was stabbed… and it affected him mentally and that’s why he had this starter gun. He wouldn’t have done anything with it.

“I picked him up. There was a fight in the street. Three people kicked a person, so James came out and said, ‘leave him alone’, and then they started attacking him.

“Then he pulled out this imitation gun. I thought ‘oh my God’. I couldn’t speak. But he doesn’t deserve an IPP for that.”

Lawrence has been out on parole five times, but has been recalled each time – for returning to a hostel late, for running away and, on other occasions, for getting drunk or using drugs.

His mother said he had told her recently that he felt like there was “no end in sight” because of the strict licensing rules after parole, so he was “falling back into old behaviours”.

He struggled with addiction and, like many other IPP prisoners who have lost hope, his mental health is a constant concern for his family.

So far, 90 IPP prisoners have taken their own lives.

Earlier this year, at HMP Erlstoke in Wiltshire, Lawrence also tried to take his own life, and it wasn’t the first time.

Miss Lawrence said: “It’s horrible – the stress of not knowing if your son is going to die.

“What I want to see happen is to sentence all IPPs, starting with the lowest rates, because otherwise they don’t have justice, they don’t have a voice, and it would be easier to go to jail.”

In a statement, a Ministry of Justice spokesman said: “It is right that IPP sentences have been abolished and we have recently terminated the lifetime licenses of 1,800 rehabilitated offenders.

“We are now exploring ways to improve access to mental health support and rehabilitation for those still in custody.

“However, with public protection our first priority, we will not continue an exercise in resentment.”

Shirley Debono, of the family campaign group IPP Committee in Action, said that by taking resentment off the table, the government was “causing more harm” to already vulnerable prisoners.

“There will be more suicides,” she said.

“They will be more self-harming and risk more violence as their hopes are cut from them.”

The IPP sentence was introduced by the then Labor government in 2005 and dropped in 2012 due to human rights concerns, but not retroactively.

Criminal justice experts and politicians have criticized IPPs as “cruel, unfair and harmful”.

The latest attempt to tackle the “unfairness” of the legislation is a Private Members (resentencing) Bill introduced by Lord Woodley in September.

Its second reading is due to take place in the House of Lords on November 15.