Video report by ITV News Scotland Correspondent Peter Smith

The family of a hit-and-run driver who killed herself while behind bars believe that their daughter would "absolutely and without a doubt" still be alive today, had she not suffered "months of bullying and horrendous mistreatment" in a young offenders' institution.

Katie Allan's mother, Linda, said her daughter was left "broken" by "horrific torture at the hands of the Scottish criminal justice system", while her father Stuart added his daughter felt as "if she was constantly being berated or constantly being harmed and ill-treated by those in the prison".

The University of Glasgow student was jailed for 16 months in March 2018 after hitting a teenage jogger and leaving the scene, having drank four pints of cider.

The 15-year-old victim suffered a broken ankle and cuts, but recovered.

Despite victim Michael Keenan's family pleading with the judge not to jail the 20-year-old, Sheriff David Pender ruled that since she had pleaded guilty to dangerous driving and drink-driving the only appropriate sentence was a custodial one.

However, when she was just one month away from being released and tagged, at the age of 21, Katie took her own life, and her parents argue it was due to the treatment she received from other inmates, and a lack of care and compassion within the prison system that contributed to this.

Katie Allan was just 21 when she took her own life. Credit: Family handout

They are now launching a legal campaign to call for an immediate review and radical reform of the Scottish Prison Service and into the provision of mental health services in young offenders institutions.

In the last five years, one of more than 500 people have taken their lives in UK prisons.

As they launched their push for reform, Katie's parents told ITV News they are doing so to get justice for their daughter and to stop what happened to them and Katie happening to others.

"Self-inflicted deaths are happening weekly in prisons in Scotland and for us if feels as if no one cares," Ms Allan said.

Katie Allan's parents believe she would still be alive if she had been treated better. Credit: Family handout

Aamer Anwar, the Allan family's solicitor called Katie's death "a tragedy" and accused the Scottish Prison Service of being "at best, negligent, and at worst, of abusing their power.

"Katie's parents want to make sure that no other family should go through what they are suffering today, that there has to be a legacy."

Aamer Anwar said no other family must go through what Katie's family have. Credit: ITV News

Speaking to ITV News, Ms Allan questioned how signs that her daughter was distressed were not picked up on by staff.

She said Katie was repeatedly strip-searched by officers at Polmont Young Offenders Institution, and questioned how they repeatedly failed to notice the scars caused by self-harming on her arms.

On her last visit to her daughter at the institution near Falkirk, the day before Katie took her own life in June, Ms Allan said her daughter was wearing a wig to hide the fact that she had lost 80% of her hair due to stress, had dark shadows underneath her eyes as she had not slept in three nights, was "distraught", "shaking, visibly frightened", and crying.

Katie was just one month away from being released on tag. Credit: ITV News

Ms Allan said that Katie had never cried in the visiting hall before since it was a very public place, and so appearing upset there "would be sign of weakness and she'd be even more of a target".

She continued: "I asked her to tell me exactly what had happened and who was bullying her and who was berating her."

Ms Allan said she urged her daughter to tell officers about what was going on, but she replied: "I can't", as she feared doing so "would endanger her more".

"What Katie went through was horrendous," her father added.

"There was no compassion, there was no care, there was no health care... and it wasn't a safe environment for Katie and it won't be for others as well.

"People that go into these places need to know they're going to come out with something, either as a better person or be educated in some sort of way, but at the moment there's absolutely none of that in what we've witnessed."

Katie's parents have questioned how signs she was suffering were not flagged up. Credit: Family handout

In response to the claims made by the Allans, the Scottish Prison Service said: "As with all prisoner deaths there will be a Fatal Accident Inquiry (FAI). We cannot comment ahead of it."

The treatment their daughter endured and her eventual death has led to the Allans campaigning for "real change" within the Scottish Prison Service, seeking a "legacy" for their daughter.

Mr Anwar said there is a "rocketing rate" of suicide in prisons, but nothing is being done about it, leading the Allans to press for change.

He continued that rather than wait "three or four years" for the report into their daughter's death to be completed and the recommendations not acted upon "there needs to be real change" and soon from the "Scottish Government into the situation and mental health provision" in prisons.

"Katie's parents are not willing to wait... and hear of another person taking their own life."

The Scottish Government - of which the Scottish Prison Service is a part -added that they too could not comment while investigations are taking place.

“It would not be appropriate to comment on the circumstances of this case pending the independent investigation which is being undertaken by the Crown and ahead of an FAI, which is an independent, judicial process that can help provide more information for families," a spokesperson said.

They added: “Our thoughts and condolences are with the family and friends of Katie Allan.

“We recognise the importance of providing a safe and secure environment for those in custody and a FAIis mandatory where someone has died in legal custody."