Retired Labor Leader Bryan Green denies he has been pushed out of the role by factional leaders and party members wanting a fresh team for the 2018 election.
Mr Green, after 19 years in Parliament and three years as leader, on Friday announced his resignation from politics effective immediately.
He had told his parliamentary colleagues of his decision on Thursday afternoon and a leadership ballot was held at 3:30am after a 12-hour parliamentary debate on the government’s forestry legislation.
Lyons MHA Rebecca White, who was nominated by Mr Green, was elected unopposed to the position.
Bass MHA Michelle O’Byrne will remain deputy leader.
Mr Green officially resigned on Friday with a visit to Government House at midday.
Mr Green was named leader after a disastrous 2014 election result for the party who lost seats in Bass, Braddon and Franklin.
“I was given the opportunity to draw the Labor Party together after what were tumultuous times,” he said.
The decision to resign comes as a shock to the many in the party, after Mr Green said he was the right person to continue to lead it when it emerged last weekend that he could face a future challenge from ousted Franklin MHA David O’Byrne.
Unions and some in the party had been lobbying for Franklin MHA Lara Giddings’ resignation so Mr O’Byrne, the former national head of United Voice, could be returned to Parliament and take leadership.
“I’ve been making this decision from the day that I took over as leader,” Mr Green said.
“My job was to stabilise the party over the past three years.
“I wanted to get us into a position where we could catapult ourselves into the next election with the necessary wherewithal and the leadership to vy for majority government in our own right.”
But Mr Green denied he was keeping the seat warm so a new leader could built up experience.
And he said factional leaders played no part in his decision.
“No-one approached me to leave; I’ve made this decision myself and I’ve made this decision in the best interests of the Labor Party,” he said.
“My view was that unless we could get to a point where this transition was made in a way that ... gave us the renewal that we needed, well then it wasn’t going to be a good day.
“Three years in, timing is everything. It’s before the budget and the government can’t call an early election before the budget.”
Mr Green paid particular tribute to former Premier Lara Giddings with whom he served in the government’s leadership during the hung parliament from 2010 to 2014, describing it as “a great honour”.
Some party members have criticised the manner in which Ms White was elected, accusing the parliamentary team of circumventing party rules by keeping the leadership vote to themselves.
Mr Green said the rule to have rank-and-file members participate in the vote wasn’t applicable when there was only one candidate in a leadership spill.
Ms White is different from many of her colleagues in that she did not come to politics through the labour or union movement, or through a political family.
Before she was elected in 2010, the 34-year-old worked as an electoral officer to former federal Labor MP Duncan Kerr and later Senator Carol Brown.
Ms White said she believed that Labor could win majority government, despite the last EMRS poll of Tasmanian voter intentions suggesting that the election could result in a hung parliament.
The poll of 1000 people from February showed that 35 per cent of them would vote Liberal, 29 per cent Labor and 19 per cent Greens if an election was to be held on that day.
Mr Green’s approval rating was 20 per cent to Premier Will Hodgman’s 52 per cent.
Ms White said she was ready to lead after serving a seven-year apprenticeship under mentors Mr Green and Ms Giddings.
A new mother to baby girl Mia, Ms White said she saw no conflicts between her new family life and new position.
“I don’t see myself as different from any other working mum,” she said.
“I’m very fortunate that I’ve got a very supportive network around me, and within me, I feel very strongly that I have an obligation to provide the best role model I can for my daughter.
“I shouldn’t let the fact that I have a young family prevent me from pursuing the ambitions I have for myself, the party, and the state.
It is still unknown if Ms Giddings will contest the next election.
Ms White said the party will open nominations for pre-selection in May.
"I'm sure at that time Lara will make her position clear," Ms White said.
Political commentator Kevin Bonham said Bryan Green’s resignation from the Labor Party leadership was inevitable, but the question of who his replacement would be was never entirely clear.
“I think that [Labor] needed to change leader before the election, given that Bryan Green was struggling to match Will Hodgman as leader,” Dr Bonham said.
“They’re seen as having a serious alternative candidate now.”
Political scientist Richard Herr said Rebecca White would be a good leader for the party.
“I think that she will be inclusivist,” Dr Herr said.
“She will be looking for ways of developing policies that are more broadly supported in the community.
“I don’t expect her to be a confrontationist.”
Premier Will Hodgman, meanwhile, said that Labor’s leadership switch-up was emblematic of the party’s alleged disunity.
“No matter what they do, how they change the leader, it won’t change the fact they’ve got no plan, they’ve got no policies, and what's happened here is another example of a Labor Party being governed by unions,” he said.