Jacqueline Morton's family have asked for an adjournment of the Fatal Accident Inquiry looking into the incident while they seek permission.

Mr Clarke, 58, was due to give evidence to the inquiry this week but relatives have said they are concerned he will not give "straight answers".

Six people were killed and 15 were injured when a Glasgow City Council bin lorry careered out of control on 22 December last year. 

The Sheriff chairing the inquiry, John Beckett QC, earlier asked legal teams representing the families to indicate whether or not they intended to pursue a private prosecution.

He wanted to know before Mr Clarke began his evidence - in case he incriminated himself.

The fatal accident inquiry has heard evidence that Mr Clarke repeatedly failed to declare a history of dizziness, fainting and blackouts on Driver Vehicle & Licensing Agency (DVLA) licence forms and in job applications to Glasgow City Council.

Launching a private prosecution would be a rare and expensive step.

Sky News reports that relatives would hope to receive legal aid as funding. Alternatives might involve private funding, or a legal firm waiving its fees. 

There would be legal obstacles too - principally the fact that a private prosecution would need the consent of Scotland's top prosecutor, the Lord Advocate, whose Crown Office has already decided that there is insufficient evidence to pursue the bin lorry driver.

In a statement regarding its decision, the Crown Office said: "It is clear on the evidence at the time that the driver lost control of the bin lorry, resulting in the tragic deaths, he was unconscious and therefore not in control of his actions. 

"He did not therefore have the necessary criminal state of mind required for a criminal prosecution. In addition, the Crown could not prove that it was foreseeable to the driver that driving on that day would result in a loss of consciousness."