LABOUR has demanded an inquiry into revelations that thousands of prosecutions have been dropped because police filed reports too late.

The party called on the national force's main watchdog to look into why nearly 4,000 offences - including alleged firearms, drink-driving and sex crimes - slipped through the justice system.

Figures obtained by The Herald under Freedom of Information laws showed that proceedings in the cases had been scrapped over six years because they were reported to the Crown Office outwith the statutory time frame.

Labour's justice spokesman, Hugh Henry MSP, said: "It's unacceptable that victims are denied justice because Police Scotland has failed to submit their case to the Crown Office in a timely manner.

"The Scottish Police Authority must hold an enquiry, and demand from Police Scotland both an explanation and a guarantee of improvement. "Victims of serious crimes deserve better from Scotland's national force."

The Scottish Police Authority (SPA) has already carried out inquiries into controversial issues such as stop-and-search tactics and the heightened visibility of armed policing in recent years.

The delays to reports to fiscals - which represent little more than one quarter of one per cent of all cases - long pre-date the current force. Police sources stress delays are often caused by third parties failing to respond to requests for information or evidence within the time frame.

The Herald figures show a total of 3,850 charges were reported to the Crown outwith the time frames between 2008/09 and 2013/14.

A total of 763 were submitted in 2013/14, the first year of the single police force, which saw the highest number of time-barred cases since 2008/09.

A total of 270,397 crimes were recorded that year, with late reports accounting for just under 0.3 per cent.

Late reports related to six underage sex charges in one six-month period and another seven firearms offences, 112 drug dealing charges and 10 animal welfare charges.

Liberal Democrat Justice spokeswoman Alison McInnes MSP said: "Anyone accused of a crime should of course have the right to due process. But victims of crime deserve justice too. The fact that nearly 4,000 prosecutions were scrapped is of significant concern.

"Ministers need to look again at the support they are offering Police Scotland to ensure that prosecutions are allowed to move forwards where they can, and Police Scotland need to explain why so many cases have dragged on and on.

"Quality of evidence should dictate whether cases come to court, not administrative efficiency, otherwise we risk letting down victims of crime."

Lawyers earlier described the delays as "astonishing" and called for Police Scotland to take action to improve their reporting procedures.

Thomas Ross QC, president of the Scottish Criminal Bar Association, said: "It seems extraordinary that they would take so long to report. If it was an isolated incident then you could accept that mistakes happen, but we're talking thousands of cases here.

"How would a victim feel if they were to ask about their case only to be told by the Crown 'we can't do anything because the police were too late in reporting it'?"

An SPA spokeswoman said: "We regularly monitors Police Scotland's performance and issues such as this are scrutinised by members at public board and committee meetings."

Deputy Chief Constable Rose Fitzpatrick defended the force, saying time-barred cases represented just a tiny fraction of the total.

She said: "In a small number of cases, where we require assistance and information from a third party, despite our best efforts, this information is not received in time."

A Scottish Government spokesperson said: "In 2013/14, more than 99.5 per cent of crimes were reported to the Crown Office within agreed timeframes.

"We are working with Police Scotland and the Crown Office to ensure that there is a clear understanding of why some cases were not submitted on time, with a view to ensuring that best practice is being followed in all cases."