The wait for a Fatal Accident Inquiry into an M9 crash that took police three days to attend has been branded “glacial and agonising” by Willie Rennie.

John Yuill, 28, and his partner Lamara Bell, 25, died after their car smashed off the road near Stirling in July 2015.

Despite a call being made to police, it took them three days to respond.

When officers finally arrived at the scene, John was dead and Lamara passed away later in hospital.

Scottish Lib Dem leader Rennie has used the fifth anniversary of the tragedy to launch a furious attack on the Crown Office for failing to hold an FAI, describing the wait being endured by the couple’s friends and family as “unforgivable”.

Police search the crash scene on the M9.

He added: “It has been five years since the accident. It has been four years since the Lord Advocate told me it would be ‘inconceivable’ not to hold an FAI ‘given the public concern over this tragedy’. I warned then the wait was already too long. I am appalled.”

Rennie repeated a call for the FAI system to be reformed, with the responsibility for carrying out investigations stripped from the Crown Office, in order to avoid other grieving families becoming “trapped in this prolonged process”.

He added: “It is time to look at removing FAIs from its responsibilities. We need a comprehensive new system of checks and balances to drive the process forward. Two families waiting years for closure is a scandal but the fact Scotland’s broken FAI system routinely does this and worse to family after family is horrifying. It is adding to their torment.

“I’ve lost count of the number of times warnings and heartache have been met with promises of change. ”

A Crown Office and Procurator Fiscal Service (COPFS) spokesman said the M9 crash investigation is still ongoing.

He added: “The case team and staff from our victim information and advice service have communicated with family members and their legal representatives throughout and will continue to keep them informed of any significant developments.”

An independent review of FAIs by HM Chief Inspector of Prosecution in August 2019 found the process was characterised by “lengthy intervals of unexplained delays” and “periods of inactivity”.

The COPFS spokesman insisted 14 additional staff – including eight lawyers – have been employed in an attempt to speed up investigations, with 58 cases closed last year, up from 42 in 2018-19.

The Sunday Mail has campaigned for years over the length of time grieving families are made to wait for FAIs.

Victims of the 2013 Clutha helicopter disaster had to wait more than five years for an inquiry, which went ahead last year.

Meanwhile, a public inquiry into the death of Sheku Bayoh is still pending almost five years ago after the 31-year-old was restrained by nine police officers using batons, CS spray and pepper spray.