Labour MSP for Midlothian, Rhona Brankin, has announced she will quit Holyrood at next year's election.
The former Scottish Executive minister said she wanted to spend more time with her family and take up other roles in public life.
She said it had been a privilege and an honour to represent her constituents.
Ms Brankin, 60, said: "After 30 years of being active in the Labour Party, I feel the time has come to step aside from frontline politics."
She served as deputy minister for culture and sport and deputy minister for environment and rural development in the early years of the Scottish Executive.
She went on to be deputy minister for health and community care and minister for communities.
Ms Brankin is a former chair of the Scottish Labour party and was a member of the Constitutional Convention that drew up the blueprint for the Scottish Parliament.
She recently took over as convener of Holyrood's Public Petitions Committee when her Labour colleague Frank McAveety stepped down after making inappropriate comments about a female spectator in the audience.
Labour leader Iain Gray said her departure would be a "big loss" to the party.
Her current Midlothian seat will disappear at the election in May next year, with a new Midlothian North and Musselburgh constituency emerging after boundary changes.