Details of the length of time it takes to set up the inquiries - known as FAIs - are contained in new data obtained by The Herald.
That shows that by March this year there were 25 inquiries in limbo - FAIs that had all been been petitioned for and granted but had not been started.
The Crown Office has said the delays are partly down to lack of court time and also because of the complexity of some medical investigations.
The data emerged as families and legal experts condemned a fresh Government-led overhaul of the FAI system which they say does not address the delays caused especially when a criminal investigation has been launched.
In one of the worst cases, families of three men who died after the Flying Phantom tug boat capsized in the River Clyde have waited more than six years for a decision on whether there will be an FAI while investigations continue.
The new Scottish Government proposals for the FAI system, launched on Monday, contains no new measures to allow decisons on inquiries to be speeded up while criminal proceedings are continuing.
But the latest data shows there remain long delays even when criminal investigations have finished or are not a factor, with waits of up to 16 months.
One death was still awaiting a court date nearly three years after the fatality. Another which happened in July 2011 had still no inquiry arranged by March.
A fatal accident inquiry into the death of toddler Declan Hainey whose remains were found at his family home in Paisley in March 2010, finally started in May.
That was 16 months after his mother Kimberley was jailed for life and ordered to serve a minimum of 15 years for his murder.
The child's mummified body was found in his cot eight months after he was last seen alive. His mother's conviction was quashed due to problems with expert evidence led by the Crown.
The Crown Office said one of the reasons for delays starting FAIs is the availability of court time, but the Scottish Court Service said it was not aware of any issues.
Officials say there can also be delays caused by the time taken to report the death.
It has emerged that in an attempt to speed up the process, the Lord Advocate issued guidance on FAIs to all procurators fiscal last December. It said a petition should be made to the relevant court within two months of receiving Crown counsel instruction to hold a fatal accident inquiry.
Scottish Labour's Patricia Ferguson, who launched a members' bill to speed up the FAI process, is concerned the new Government proposals still do not address all the outstanding issues. She said: "There needs to be a fundamental overhaul of the system if it is to deliver for bereaved families."
A Crown Office spokesman said: "The Scottish Fatalities Investigation Unit works to ensure that deaths investigations are carried out as quickly and efficiently as possible.
"However there are a number of factors that contribute to the time taken for a fatal accident inquiry to commence.
"One such factor is that in some cases there can be a delay between the date of death and it being reported [to the Crown Office]. This can arise because the circumstances do not at first give rise to concern to relatives of the deceased but they later report concerns."
A Scottish Court Service spokesman said it was unaware of any issues over lack of court time and if planned properly, there should be no delay. With large, long-running inquiries the court services uses premises outside courts.