Senior federal Labor MP Kate Ellis of Adelaide has stepped down from the party's frontbench and will not contest her seat, leaving politics at the next election.

The move will require a reshuffle in the shadow cabinet, as Ms. Ellis was Labor's spokeswoman for Early Childhood and Development.  As it turns out, childhood development plays a large role in her decision - she doesn't want to split her time between two cities just as her two year old son prepares to enter school.

"The simple truth is that I just cannot bear the thought of spending at least 20 weeks of every year in Canberra away from him and the rest of my family," the 39-year old wrote in a letter to constituents.  "When I think about having to regularly miss things like his first day at school, his presentations at school assembly, a first sporting match or even just being there for him when he is sick and wants his mum, I know that it would make me absolutely miserable."

The opposition must decide how much of a shake-up is necessary at the present time.  Meanwhile, Bill Shorten has nothing but glowing words for his "trusted adviser and a true friend". 

"We know how hard she works and we admire her strengths as a policy thinker, as a campaigner and as a trailblazer," he said in a statement.  "But we also know Kate wants the chance to spend precious time with her son Sam.  We respect her decision."