Kezia Dugdale has announced she will resign as an MSP at the end of the current session of the Scottish Parliament.
The Lothian list MSP, who was leader of the party from 2015 until 2017, is to take up a post as director of the John Smith Centre for Public Service at Glasgow University.
In a statement released on Tuesday, Ms Dugdale said her next task is to “rebuild faith in our politics”.
“It has been an honour to represent the Lothian region for Labour in the Scottish Parliament and to have had the opportunity to serve the party in a variety of roles for over a decade – from party organiser to leader,” she said.
“All through that time the passion and commitment of our members has been inspirational.
“No matter how difficult things were, activists were always willing to hit the doorsteps to spread Labour’s message.”
She added: “I have devoted my working life to public service and this is an incredibly exciting new opportunity for me to lead the work of the John Smith Centre.
“Throughout my career I have taken on tough and challenging tasks and my next task is to rebuild faith in our politics.
“Disruptive events and the rise of populism has led to increasingly polarised and emotional politics where rational, evidence-based thinking has lost its standing.
“Faith in public service, politics and the political process has to be restored and that progress must be sustainable.
“John Smith said ‘the opportunity to serve our country – that is all we ask’.
“It will be an honour to build on his legacy and inspire his values of public service in a new generation.”
First Minister Nicola Sturgeon said Ms Dugdale would be a “big loss” to both Scottish Labour and the Scottish Parliament.
She added: “I hope she enjoys her new challenge.”
Ms Dugdale has previously voiced her concern over her party’s stance on Brexit and has been critical of Labour leader Jeremy Corbyn.
After her resignation as Scottish Labour leader in 2017, she took part in the ITV programme ‘I’m a Celebrity … Get Me Out of Here’, which she was reprimanded for.
Two weeks ago, Ms Dugdale won a defamation case brought against her by Wings Over Scotland blogger Stuart Campbell over a column she wrote in 2017.
Mr Campbell sought damages over her claims that he had written “homophobic tweets”.
She won the case after a sheriff ruled her comments had been “fair” despite Ms Dugdale being incorrect to imply Mr Campbell is homophobic.
Scottish Labour leader Richard Leonard said: “Kezia will be a loss to the Scottish Labour Party but I am sure she will still play a valuable role in public life going forward.
“Kezia stepped forward at a difficult time for the Scottish Labour Party and on many issues – from arguing to use the tax and social security powers of Holyrood to making the case for federalism, she helped the party rebuild after the devastating losses of the 2015 General Election.
“On behalf of the Scottish Labour party, I thank Kezia for her service and wish her well in the next exciting chapter of her life.”
Speaking at a press conference in the Scottish Parliament following the announcement, Ms Dugdale said the opportunity was not one she could allow to pass by.
“I wasn’t looking to leave, I genuinely wasn’t,” she said.
“I love being an MSP and it’s going to be really hard to leave in the middle of July.
“But I’m leaving to do something I consider to be really important.
“I believe in politics, I believe that politicians are good people doing really good, critical, important work and I want to do more to help showcase that.”