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The chief constable of Durham has announced he is to retire this summer.

Mike Barton, who has led the force for seven years, revealed he will step down on 7 June.

He said the time had come to "hand the baton to the next generation of talented and committed people".

The force said details of the recruitment process to find Mr Barton's successor will be announced in the coming months.

He joined Durham Constabulary in 2008 as assistant chief constable and was promoted to deputy chief constable the following year.

In a letter to Durham's Police, Crime and Victims' Commissioner, Ron Hogg, Ch Con Barton said: "There remain many challenges in policing that I would have relished tackling, but there comes a time when one should hand the baton to the next generation of talented and committed people who will bring their own style, thinking and approach."

'Deep frustration'

Since taking up the role Mr Barton has repeatedly called for debate over the approach to tackling drug addiction.

He recommended addicts be given free heroin and supplied with clean needles in a safe environment known as a "consumption room".

In his letter, the 62-year-old said he hoped for "sensible conversations about how the current approach to controlled drugs is not working".

He added: "It remains a lingering sadness and deep frustration that heroin-assisted treatment for heroin addicts is not de rigueur."

That stance is shared by Mr Hogg.

He described Mr Barton's leadership of the force as "unique and unequivocal" and said he had been "very fortunate to have such a dedicated, forward-thinking and passionate" chief constable.

The force has achieved three successive Outstanding ratings in annual police effectiveness inspections.