Prime Minister Julia Gillard has put the vexed issue of gender equality back on the agenda by asking the Human Rights Commission to look into workplace discrimination against women who have children.

Attorney-General Mark Dreyfus wants to reduce workplace discrimination against pregnant women and parents, particularly mothers, returning to work after parental leave.

"There is significant anecdotal evidence that women are being demoted, sacked, or having their role or hours unfavourably restructured while on parental leave or on their return from leave," he told AM.

The Government has asked Sex Discrimination Commissioner Elizabeth Broderick to oversee an inquiry to measure how often the discrimination is happening, what is driving it, and what the consequences are.

Key points: Federal Government announces inquiry into workplace discrimination against working mothers.

Federal Government announces inquiry into workplace discrimination against working mothers. Inquiry to focus on pregnant women, parents and those returning from parental leave.

Inquiry to focus on pregnant women, parents and those returning from parental leave. Sex Discrimination Commissioner to oversee the inquiry

Sex Discrimination Commissioner to oversee the inquiry Commissioner to consult with employers, unions, industry and women's groups.

Commissioner to consult with employers, unions, industry and women's groups. Interim report due in October, final report due in May next year.

"The Bureau of Statistics did a very big survey in 2011 in which 67,000 women reported experiencing some form of discrimination in the workplace while pregnant - that's staggering," Mr Dreyfus said.

"The data also shows that nearly a third of women with a child under two permanently left the workforce while pregnant or just after having a child.

"Some will have chosen to do that voluntarily but we know that too many leave involuntarily because they're offered a full-time or nothing choice or they're demoted or sacked.

"This is unacceptable, it's unproductive, and often unlawful."

An interim report is due in October, with the final report due in May next year.

Women reluctant to speak up against discrimination

Ms Broderick says her first task will be to consult widely with employers, unions, industry groups, and women's groups.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 3 minutes 58 seconds 3 m 58 s Discrimination against pregnant women investigated ( Alexandra Kirk ) Download 1.8 MB

"We do know that pregnancy discrimination is an issue in Australia - 21 per cent of our own complaints relate to pregnancy discrimination and also a similar amount - 21 per cent - of the Fair Work Commission's complaints relate to it as well," she said.

"I think because we're still really connected to what I call the ideal worker model, and the ideal worker in Australia - and there's good research on this now - is someone who works 24/7, no visible caring responsibilities, and as a result of that, male.

"So while that model is the predominant model for Australian workplaces, I think pregnancy discrimination may continue to exist."

She says many women are reluctant to take action for a number of reasons.

"One thing particularly with pregnancy discrimination is that it's often at the time that their whole life is changing; there's a new person entering the world and all their attention is focused on that," she said.

"They know it's not right, but in some sense they just don't have time to do anything about it, and speaking out will potentially leave them open also to victimisation."

Union welcomes inquiry, says problem endemic

Sorry, this video has expired ACTU president Ged Kearney speaks to ABC News 24

Australian Council of Trade Union president Ged Kearney has welcomed the inquiry, saying discrimination against women with families has been endemic for years.

"So many women are sacrificing careers, secure jobs and decent work simply because they have families," she told News 24.

"They have been telling us this for a long time and now we can start on the path to doing something serious about it."

Mr Dreyfus says the results of the inquiry will determine whether extra reform is needed.