THE aunt of a young girl who died when a driver blacked out at the wheel in Glasgow has accused the Crown Office of "washing their hands of another driver who has killed people."

Catherine Cairney, the aunt of 20-year-old Laura Stewart who was killed in 2010 along with her friend Mhairi Convy in Hanover Street, in Glasgow, spoke out after bin lorry driver Harry Clarke apologised in a BBC documentary.

In the Lies, Laws and Bin Lorry Tragedy, Mr Clarke issued his first 'unreserved apology' for his role in the tragedy which killed Erin McQuade, 18, her grandparents Jack Sweeney, 68, and his 69-year-old wife Lorraine, from Dumbarton, West Dunbartonshire, Stephenie Tait, 29, and Jacqueline Morton, 51, both from Glasgow, and Gillian Ewing, 52.

He said he had always intended to answer all questions put to him at the Fatal Accident Inquiry (FAI)into the tragedy but did not because of "a direct result of legal advice given to me at the time."

Miss Cairney said Mr Clarke's apology, broadcast on Tuesday night, was almost a side issue and the lack of a prosecution was key.

She said: "The real story is that the Crown Office have washed their hands of yet another driver who has killed people.

"It's a whitewash. It's the same excuses, the same egos, the same slap dash attitude to justice, the same systematic failures.

"We have no faith in the system or the people at the top of it."

She said the driver in the crash that killed her niece had suffered six previous black-outs but had not been charged. He was ruled to have suffered 'a simple faint.'

"There has to be a change in the law," she added. "How many more people have to die on the streets of Glasgow before someone does something about it?

"When I heard the solicitor for the family of Stephenie Tait say it was about not having any more families go through this, it broke my heart.

"Here are more families, going through this, five years after Laura and Mhairi were killed."

The families of the two girls have lodged a 21 page complaint with the Solicitor General about the way the case was dealt with by the authorities, she added.

Hours after the documentary aired, a petition was lodged with change.org calling for the decision not to prosecute Mr Clarke to be reviewed.

It says it was "made prematurely and in bad judgement."

Petitioner Beverly Petrie, from Inverness, said she would submit her petition to Justice Secretary Michael Matheson.

A spokeswoman for the Scottish government said the decision to prosecute, however, was a matter for the Crown Office and not for Mr Matheson.

Lord Advocate Frank Mulholland QC has said he has “no doubt” it was the right decision not to prosecute.

Prosecutors would have to prove Mr Clarke was in control of the vehicle at the time of the incident but, because he was unconscious, he was not in control, so “the necessary criminal intention” was not present.

Mr Mulholland argued there was insufficient evidence to establish “foreseeability” and prove Mr Clarke knew he was unsafe to drive that day.

He said: “I have no doubt that you cannot establish, cannot prove, that Mr Clarke knew that he was unfit to drive that day as a result of an ongoing medical condition. If you can’t prove that, you cannot prove criminal intention.”

The Crown Office last night denied claims a top prosecutor described Mr Clarke as a "fat, uneducated man" who "didn't know any better."

The allegations were aired in the documentary when the daughter of victim Gillian Ewing, from Edinburgh, said senior prosecutor David Green, head of the Scottish Fatalities Investigation Unit, made the remarks when he met families.

Lucy Ewing, 22, said she challenged Mr Green over the fact that Mr Clarke kept quiet about suffering a blackout when he renewed his HGV licence in 2012.

She said: "I said; 'So he lied.' David Green said; 'No, he didn't tell the truth. I said; 'That's the same thing as lying.

"I was promptly told; 'The thing you don't know about Mr Clarke is he is a fat, uneducated west of Scotland man and doesn't know any better.

"I'm not defending Harry Clarke but that's not a very nice thing to say about anybody, and it's not very professional either."

In a statement, a spokesman for the Crown Office said: "Our official who met the families is highly experienced in meeting bereaved families and has never been known to use such language in his many years in public service.

"He has categorically denied making the remark attributed to him. The fact he did not say this has been confirmed by another official who was present."