Alex Salmond has backed a private prosecution of the driver involved in the Glasgow bin lorry crash that killed six people.

The former first minister said families had an absolute right to try to pursue Harry Clarke, 58, who killed six people and injured 15 more in Glasgow before Christmas 2014.

But Mr Salmond also supported Lord Advocate Frank Mulholland, who yesterday refused to back a private prosecution of Mr Clarke and another motorist who killed pedestrians after blacking out at the wheel.

Asked about Mr Mulholland's decision on his weekly radio show, Mr Salmond said: "If there is a reason for him not being able to take forward a prosecution in terms of law, it will be a good one.

“Whether the law is right or wrong is another matter.”

Quizzed about private prosecutions, he said: "I think the family have the absolute right to do it.

"In my own opinion, yes, go for the private prosecution."

The Crown has always argued that there was not enough evidence to show that a crime was committed by Mr Clarke.

A Fatal Accident Inquiry (FAI) held last year heard that Mr Clarke lost consciousness at the wheel and that he had a history of health issues - including a previous blackout in 2010 when at the wheel of a stationary bus - but had not disclosed his medical background to his employers or the DVLA.

Solicitors representing the relatives of three of the six bin lorry victims - Erin McQuade, 18, and her grandparents Jack and Lorraine Sweeney - will still ask for a court to allow a private criminal case against Mr Clarke.

But their chances of securing the right to do so - the first since 1984 - are thought to be slim after Mr Mulholland withheld support.

The Lord Advocate, Frank Mulholland, on Wednesday also has refused a request for a private prosecution of motorist William Payne, who killed Mhairi Convy, 18, and Laura Stewart, 20, in December 2010, in North Hanover Street, Glasgow.

Like Mr Clarke, Mr Payne had lost consciousness.

A spokesman for the Crown Office said: "The Lord Advocate has declined to grant concurrence to the bill for criminal letters seeking a private prosecution of the driver of the bin lorry involved in the George Square fatalities on December 22, 2014.

"The original decision not to take criminal proceedings was made on the basis that there was insufficient evidence in law to prove that a crime had been committed and that position remains unchanged."

The spokesman made an almost identical statement about the North Hanover Street crash.

An FAI held in 2014 found that "reasonable precautions" could have prevented the deaths of Ms Convy and Ms Stewart.

Mr Payne appeared in court accused of causing death by dangerous driving but the case against him was dropped.

A spokesman for Digby Brown, the firm which represents the families of Ms Convy and Ms Stewart, said he was not surprised by the Lord Advocate's ruling.

He added: "It is the families' intention to go forward to a high court hearing and ruling on the issue.

"Our hope is this would be held in the same timescale as the bin lorry question as many of the legal issues and questions about the crown's decision making across the two are similar."