The families of two girls who were killed by a driver who blacked out at the wheel have said they may also consider a private prosecution if legal action relating to the fatal bin lorry crash is successful.

Laura Stewart, 18, and Mhairi Convy, 20, were knocked down and killed when driver William Payne passed out at the wheel of his 4x4 in Glasgow in December 2010.

A Fatal Accident Inquiry was held and the Crown Office decided not to prosecute Mr Payne, who had lied to the DVLA about his medical history in a similar way to bin lorry driver Harry Clarke.

The family of three of the victims in the bin lorry crash have confirmed they plan to launch a bid to put Mr Clarke in the dock.

Catherine Cairney, the aunt of Miss Stewart who speaks on behalf on both families, has now said they too would consider such a move if the bin lorry relatives are successful.

"If they get the go-ahead for that, that opens up the door to a lot of families who feel they have been let down by the Crown," she said.

"I think we would certainly look at that with interest, but there's a long way to go with it and I think the odds are stacked against them unfortunately."

She added that the Stewart and Convy families have been in touch with relatives of the bin lorry victims and plan to meet them in the New Year. They are also in contact with the family of Jim Lochrie, the bus driver who was killed when his colleague David Logue blacked out at the wheel and knocked him down in March 2012.

Mr Logue had also failed to disclose previous medical incidents to the DVLA.

Ms Cairney said: "When Payne was not prosecuted, that set the precedent and they couldn't prosecute anybody else presenting with the same circumstances.

"As far as we're concerned, the Crown Office had the ability to prosecute Payne, Logue and Clarke and they chose not to.

"They let all of these families down."

In all three cases an FAI was held which showed that the drivers either lied or failed to tell the DVLA about medical problems.

Ms Cairney added: "For us, FAIs are just a tick-the-box exercise and nothing ever really gets done.

"They are supposed to be about learning lessons and ensuring the same things don't happen again, but William Payne killed our two girls five years ago and here we are again."

The family of Erin McQuade and Jack and Lorraine Sweeney are seeking the private prosecution against Mr Clarke and said on Monday that their solicitor had written to the Lord Advocate Frank Mulholland and the Justice Secretary Michael Matheson.

The action is understood to be backed by the family of Jacqueline Morton, who was also killed when the Mr Clarke lost control of the lorry in Glasgow's George Square on December 22 last year.

Stephenie Tait and Gillian Ewing also lost their lives.

The Crown Office said on Wednesday it had not received any letter from the McQuade family's lawyer and refused to speculate on what their response might be.

However, legal experts claim that officials would have to object to the proceedings as they have been so outspoken in their defence of the decision not to prosecute.

The Crown - who assert that all cases are dealt with based on their own circumstances - also said there was "insufficient evidence in law" to raise criminal proceedings against Mr Payne.

A spokesman added: "A recent review of that decision was undertaken by independent Crown Counsel, who was unconnected to the original case, and the original decision not to prosecute was upheld."

Meanwhile, it has been revealed that George Square will fall silent as a mark of respect on the anniversary of the tragedy, with the Christmas amusements, including the ice rink, closing over the time that the accident occurred.

A council spokesman said: "Glasgow Life has not taken any bookings for the ice rink or other attractions that coincide with the time of the accident last year. This means the ice rink will not be in use 2-3pm and the carnival rides will not run 2.15-2.45pm."