John Finnie, the politician who quit the SNP over its decision to end its opposition to Nato, has said he will stand down at the next Holyrood elections.
Mr Finnie, who has been an MSP for eight years, said the 2021 elections was the "right time to step aside".
He will retire from front-line politics shortly after his Member's Bill, which will ban the smacking of children in Scotland, is passed by the Scottish Parliament.
Mr Finnie, a former police dog handler, was first elected to Holyrood in 2011 as an SNP MSP. He had joined the party at the age of 16, but after a decision was made to overturn its long-stand opposition to Nato, he quit the SNP after 43 years of membership, in a move he described as "hear-wrenching".
He then sat as an independent MSP for four years before winning a Highlands and Islands list seat for the Scottish Greens in 2016.
Today Mr Finnie, whose daughter Ruth Maguire is an SNP MSP, said he would not seek a further term.
He said: “It is an honour to serve the Highlands and Islands in the Scottish Parliament and I intend continuing to work hard until my last day in office.
“I’ve been involved in representative politics since being elected a Highland councillor in 2007 and enjoyed helping people, but I feel the time is right to step aside and let others bring their energy and ideas to what is a demanding job."
The Scottish Green Party has started its candidate selections for the 2021 election seeking to improve on the six MSPs it returned to Holyrood in 2016.
Mr Finnie added: “Throughout my time in Parliament, I’ve put my home region of the Highlands and Islands and my constituents at the forefront of my work. Driven by my interest in social and environmental justice, I have been pleased to secure a number of concessions and legislative changes to improve the lives of people in the region.
“At this time, I’m focused on working with others to secure the passage of my Member’s Bill giving children equal protection from assault and hope to see it become law in the near future.
“The Climate Emergency our planet is facing means that, more than ever, Green policies are required. I know there are others who can ensure they are promoted, and delivered, for my home, the Highlands and Islands of Scotland. Meanwhile, I look forward to having more time to spend with my family.”