Labor frontbencher Kate Ellis is set to quit politics at the next election after more than a decade in federal parliament to spend more time with her young son.
Ms Ellis will also step down from the shadow ministry shortly, creating a vacancy in the early childhood education portfolio for Bill Shorten to fill, but will serve the remainder of this term and not force a byelection.
As she announced her decision to quit the seat of Adelaide - which she held at the 2016 election with a margin of 4.7 per cent - Ms Ellis re-opened debate about the pressures of juggling family life with the demands of federal politics for men and women.
Ms Ellis, who is just 39, is married to Adelaide media identity David Penberthy and the pair have three children, including a toddler.
Talk has already turned in the ALP to who might replace Ms Ellis on the front bench, with speculation centring on fellow South Australian MP Amanda Rishworth as a front-runner to move from the outer shadow ministry to the shadow cabinet. That move could then see fellow South Australian MP Nick Champion move from the shadow assistant ministry to the outer ministry.
However, at least three others from the outer shadow ministry - Linda Burney, Ed Husic and Clare O'Neil - could also lay claim for promotion to the shadow cabinet and Labor sources have told Fairfax Media they will not rush to replace Ms Ellis.
Ms Ellis said she had made the decision to quit at the next election for one reason: "I feel like, honestly, I still have much more to give. However, it just became really apparent to me that I've been incredibly lucky that, since becoming a mother, when my child's been a baby, I've been able to travel with him. I've been able to have flexibility in this role that most people don't get. But during the next parliamentary term, he'll start school".
"He'll need to be in Adelaide. And I will need to be in Canberra if I'm the member for Adelaide, and that's a really big problem for me and for our family."
"This is something that every member of parliament, whether they are a mother or a father, has to juggle and has to make decisions with their family about what works for them. Just today I have heard from many MPs or ex-MPs, male and female, who have had the same sort of pressures and some who wish they had made the same decision."
"I would hate for my legacy to be sending a message that you can't be a young woman and go into federal parliament because I've made this choice."
Junior Liberal minister Alex Hawke, who has himself recently become a father again, tweeted he was sorry to see Ms Ellis quit and that "in 2017 more could get done in less sitting weeks if we modernised parliament. Vital for mum and dad MPs of [the] future".
Ms Ellis, who was elected in 2004 in a poll that saw Labor lose ground to John Howard's Coalition government, has spent most her career on the front bench in government and opposition.
She lost the senior shadow education portfolio after the 2016 election but remained in the shadow cabinet.
Ms Ellis did not rule out a future run for the South Australian parliament but said she had no plan to do so.
She is allied with the powerful Shop, Distributive and Allied Workers union, which is an influential player in Labor's right faction in South Australia.
Mr Shorten paid tribute to Ms Ellis' and praised her as a "policy thinker, as a campaigner and as a trailblazer".
"A champion for education - from early childhood to schools, skills and universities - Kate speaks with passion, understanding and experience, of how great education can transform lives and empower people to fulfil their potential," he said.
