A Labour MSP is leaving Holyrood to take up a senior post in the trade union movement.
John Park said he is leaving to fight for workers' rights "at the coal face" as policy and strategy director of the Community trade union.
The Mid Scotland and Fife regional MSP, first elected in 2007, will be replaced by the next Labour candidate on the regional list, Jayne Baxter.
Mr Park, who formally notified the Presiding Officer of his pending departure this Friday, said: "Representing the people of Mid Scotland and Fife has been an enormous privilege and I am really grateful to have had that opportunity.
"I want to thank everyone who voted for me and Labour party members for the support they have given me. This is a decision that I have not made lightly and I now have the opportunity to represent thousands of workers across the UK.
"I've tried to use my time in politics to make sure the issues important to working people, jobs, apprenticeships and a living wage, are centre-stage. Now, as workers are under attack like never before, I am returning to my union roots to fight at the coal face.
"I wish Johann, who has been a good friend to me, and all my friends in the Labour group the very best for the referendum and upcoming elections. I am a strong Labour supporter who loves my country, so will be campaigning shoulder to shoulder with them in the months and years ahead.
"I would also like to thank Holyrood officials and my own staff who are undoubtedly the most dedicated group of people I have ever met. Their support and assistance has been invaluable."
Unlike constituency MSPs, who are elected on a first-past-the-post system, regional MSPs are selected by the number of votes the party receives on the second ballot during Holyrood elections. Departing MSPs are subsequently replaced by a party member lower down the list. Mr Park said: "I know Jayne Baxter and I've no doubt she will be a hardworking and diligent MSP."
The general secretary of Community, Michael Leahy, said: "I know this has been a difficult decision for John but I am delighted that he is returning to the trade union movement. His voice will be a powerful addition for our members. John's considerable experience of public life and getting things done will ensure that Community trade union are better equipped to represent working people in Scotland and right across the UK."