Labour MP Sue Moroney has announced she won't be standing for Parliament at this year's election.
In a statement, the Hamilton-based list MP said she'd lost support of the party's ruling council "for an electable position on the Labour Party list".
She has been an MP since 2005, and was 10th on the party's list at the 2011 and 2014 elections. She was promoted to the party's shadow cabinet by leader Andrew Little in November 2015.
"I am grateful that I have had the opportunity to fight for the rights of children, working families, women and the people of Hamilton.
"I'm proud to have extended paid parental leave, achieved mandated meal breaks and rest periods for workers and fought early childhood education cuts, amongst other things."
She said the next phase of her life would be spent "pursuing equality and social justice", even outside Parliament.
"Sue has been a hard-working and dedicated MP who can look back with pride on her achievements during her 12 years in Parliament," said Mr Little.
"We will certainly miss her contribution in the Labour caucus and wish her all the best for the future."
She will serve out the rest of her term in Parliament.