Scotland's top inspector of policing has announced he is to retire next year.

Derek Penman, HM Chief Inspector of Constabulary in Scotland, has given notice to the Scottish Government that he intends to retire on March 31, 2018.

Mr Penman has spent 33 years in policing, and was appointed HM Chief Inspector of Constabulary on January 31, 2014.

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He said: "I am proud to have led HMICS for almost four years, during which time I have consistently sought to improve policing across Scotland, addressing significant issues and making recommendations for change through the publication of over 30 inspection reports.

"Having re-established HMICS as a key scrutiny body in the new policing landscape, the time is now right for me to move on to new professional challenges.

"I have given the Scottish Government early notice of my intention to allow them sufficient time to recruit and appoint my successor.

"During my remaining time in post, I am keen to focus on supporting the new Chair and Chief Executive of the Scottish Police Authority and the executive team of Police Scotland in addressing current priorities."

HM Inspector of Constabulary in Scotland is the senior professional police adviser to Scottish ministers.

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Justice Secretary Michael Matheson said: "I am very grateful to Derek for his unstinting service to the public over 33 years in policing, including nearly four years as HM Chief Inspector for Scotland.

"In his Inspectorate role, he has provided significant, independent oversight and challenge to the service and the Scottish Police Authority, at a key time for policing.

"His scrutiny work, including key reviews and reports have resulted in, and continue to underpin, important improvements to how Scotland's unified national police service safeguards the public and keeps communities safe.

"As Derek observed in his most recent independent annual report, policing performance in Scotland remains strong, with officers and staff strongly committed to providing a good service for all of Scotland's communities.

"He can be proud of the contribution which the Inspectorate under his leadership has made to the on-going improvements in policing in Scotland.

"I am sure that in his remaining months in post he will continue to make a significant contribution. I wish well for his retirement when it comes."