The Scottish Police Authority (SPA) and Police Scotland have failed to deliver improvements to forensic services, a watchdog has concluded.

HM Inspectorate of Constabulary in Scotland (HMICS) found there has been no strategy in place for the delivery of forensic services in Scotland for more than four years.

A HMICS report on how the service is managed and delivered by the SPA makes 23 recommendations for improvement.

Key findings published in advance of the full report state that while the quality of forensic work undertaken in Scotland is good, the SPA "has not provided strategic leadership" and "has not put in place a clearly-established strategy, investment plan and joint planning cycle".

HMICS also identified "weaknesses" in the strategic engagement with Police Scotland and the Crown Office and Procurator Fiscal Service.

It found forensic services were "consistently working above capacity" with levels of demand coupled with the geographical spread of staff and functional structures presenting "major challenges" for leadership, management and staff morale.

The report highlights "weak communication and engagement between management, staff and unions", and ongoing challenging financial circumstances.

The operating budget for forensic services was £27.7 million in 2016-17, just 2.6% of the overall SPA policing budget.

Gill Imery, assistant inspector of constabulary at HMICS, who led the review, said: "The service has been subject to continual change over the past ten years and has done well to innovate and meet increasing demands from those who use its services.

"However, it was concerning that our inspection found there has been a lack of progress across improvement areas which were previously highlighted to both the SPA and Police Scotland."

SPA board member Nicola Marchant said: "This HMICS report highlights that Scotland benefits from a forensic service which has increased its output, is delivering to a high quality and has benefited from significant investment in technology and modern facilities.

"However, clearly there are implications and a number of steps required to achieve the recommended approach and this will take time to progress."

Police Scotland Detective Chief Superintendent Sean Scott said: "Police Scotland welcomes the independent scrutiny from the HMICS report into forensic services and we look forward to working with the SPA and other partners in reviewing and taking these recommendations forward."