Presiding Office Ken Macintosh has announced he is to leave Holyrood at next year’s elections, after more than two decades as an MSP.
Mr Macintosh said that “after much reflection” he had decided not to stand again.
He said it had been an “honour” to have been an MSP since the devolved Scottish Parliament had been established – adding that the institution had “grown in confidence and maturity”.
But he said there were also “clearly many challenges which lie ahead”.
He stated: “The privilege of being Presiding Officer in this, my now final term, is something I will never forget and I will continue to do what I can to support the Parliament and the hopes and ambitions it sustains for our democracy.”
Mr Macintosh was voted in as the MSP for Eastwood in 1999, holding the seat in the next three Holyrood elections.
When the Scottish Conservatives enjoyed their best ever election result in 2016 he lost the seat to Jackson Carlaw but was still returned to the Parliament as an MSP for the West of Scotland region.
After that Mr Macintosh, who was elected as a Labour MSP, took on the politically neutral role of being Holyrood’s Presiding Officer.
In his time in the Scottish Parliament, Mr Macintosh, who was a television producer with BBC News before being elected, has served as a ministerial aide to former first minister Jack McConnell, and also successfully introduced a Member’s Bill bringing in tougher regulations for sunbed parlours in a bid to help tackle skin cancer.
He ran twice to be leader of the Scottish Labour Party, standing for the post unsuccessfully in 2011 and 2015.
In a statement the father of six said he had first stood for election in 1999 because he “believed that the new Scottish Parliament offered so much to our country, not least a fresh way of approaching politics”.
He added: “I have always felt honoured to carry that democratic torch as an elected representative and never more so than when chosen by my peers to become Presiding Officer.
“I can say with all honesty I am proud of what we have achieved over those two decades, from land reform and the smoking ban to the investment in our public services and public servants.”
He added: “I believe the Scottish Parliament has delivered on so much of that early promise but I am conscious too that the threat to democratic politics and our liberal society looms as large as it has ever done.”
Scottish Labour leader, Richard Leonard paid tribute to Mr Macintosh, saying: “Ken has been a great servant of the Scottish Labour Party, the Parliament and most important of all, the people.
“An ardent supporter of devolution, and a member of the Parliament since 1999 his unstinting efforts as a Labour front bencher and over the last four years as the Presiding Officer have consistently made the case for the Parliament as a power for change.
“He is a kind and decent man with a strong sense of his own values. The Scottish Labour Party wishes him, Claire and the family well.”