LESS than half of all working women are entitled to paid maternity leave, and those that are entitled need it the least, official figures from the Bureau of Statistics show.

While there has been an increase in the proportion of working women entitled to paid leave after childbirth, from 31 per cent to 45 per cent in the five years to last August, experts say progress is too slow.

"If men had babies, this would not be happening," said Barbara Pocock, the director of the Centre for Work and Life at the University of South Australia.

But women are also divided in their access to paid leave.

The figures show that high-income earning women in professional jobs in government, finance and education were most likely to be entitled to paid leave.

"It is ironic that the higher-paid households have access to a higher level of paid maternity leave, and the ones who really need it have the least level of support," Dr Pocock said.

The figures suggest an increase in inequality between women over the five years.

The Bureau of Statistics says: "Increases in paid maternity leave entitlements were concentrated among the higher earners, with only small increases in paid maternity leave entitlements for female employees earning under $1000 per week."

The average annual income of women entitled to paid leave was $47,000, compared with an average of $25,000 for women who are not.

Two-thirds of women who worked full-time were entitled to paid leave, compared with less than a third of part-timers.

A Productivity Commission inquiry into paid maternity leave is due to report to the Federal Government in September.

The commission has heard a range of proposals from union and employer groups, including one for a 14-week publicly funded maternity leave scheme paid at the minimum wage.

Dr Pocock said increasing access to paid maternity leave would not only help lift the economy, by enabling employers to retain well-qualified staff, but also improve maternal and infant health.

"We save babies lives when we give women a rest after birth," she said.