Australian children have poorer health and education outcomes than Latvia, Slovenia and Croatia, a new report from UNICEF has revealed.

The Fairness for Children report, released on Thursday, shows Australia ranks 27th out of 35 in health equality outcomes among OECD countries and 24th out of 37 in education equality results.

National Children's Commissioner Megan Mitchell said Australia was failing to give all children the best start in life.

"UNICEF's report highlights the widening gap between children at the bottom and those in the middle," Ms Mitchell said. "The report asks challenging questions for Australia's policymakers on how to address the needs of our most vulnerable children."