Australia's workplace watchdog has revealed that pregnancy discrimination is now the number one complaint against the nation's employers.

The Fair Work Ombudsman says its figures indicate that for the first time there were more complaints about pregnancy-related discrimination in 2013 than for complaints related to mental or physical disability.

Business analysts say it is yet another indication that far too many employers have archaic misperceptions about women, and need to build more flexible workplaces.

Of the 235 complaints to ombudsman, 28 per cent were from pregnant women and 21 per cent were from people with physical or mental disabilities.

Around 11 per cent felt their family or carer responsibilities resulted in them being treated differently.

The commission investigated 76 matters, took three to court and executed enforceable orders in another three.

Sex Discrimination Commissioner Elizabeth Broderick says it shows employer attitudes must change.

"I think the key message is that pregnancy discrimination is still alive and well in Australian workplaces," she said.

Ms Broderick says attitudes need to change.

"Women represent more than 50 per cent of the Australian population. They represent half the talent pool that exists in this country," she said.

"And smart employers understand that actually, keeping women attached to the labour market through flexible work arrangements, through parental leave, whether it's the national scheme or a private scheme, they're important strategies to ensure that all people can contribute to the productivity and stronger economy of this country."

ACTU president says bias against women rife

Under Australian workplace laws, women have a legal right to take maternity leave as well as the right to return to the job they left.

Employers are not allowed to make a woman feel uncomfortable about being pregnant, and must modify any shifts or tasks that could become difficult to complete.

The Australian Council of Trade Union's president, Ged Kearney, says it is clear these laws are not always obeyed.

She says pregnancy discrimination can happen in a variety of ways.

"Discrimination actually whilst pregnant, at work, where, for example, women are not allowed to get lighter duties in the later pregnancy," she said.

"They are not allowed extra toilet breaks, with dire consequences. We have heard of a number of professional women experiences along the lines of handing in a request for maternity leave and being told that they might as well be handing in a resignation letter."

Ms Kearney says archaic attitudes towards women do not belong in modern workplaces.

"I think it's a deep-seated bias against women with children being in the workforce. I don't know, maybe it goes back to the '50s and '60s," she said.

"It certainly goes back to the fact that I think a lot of men now are in are still in predominantly in managerial positions."

But she says there are many employers who realise the value of providing a flexible workplace.

"We've got lots of employers out there who are now offering incentives for women to come back after maternity leave," she said.

"They're giving them bonuses and offering to subsidise childcare because finally, I think, many employers are seeing the benefits to the business of having skilled women back in the workforce with that corporate knowledge and with that loyalty."

Sex Discrimination Commissioner says role of fathers also important

Ms Broderick is travelling around the country to teach people how to deal with discrimination and educating employers on good habits and practices.

She says it is important for the health of the economy for workplaces to be able to help employees balance work and family.

"We need to be in the mindset which recognises that women and men need to work and care and we need to work to make that fit together," she said.

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She says men also need to be recognised.

"By recognising men and their caring responsibilities, it sends a strong message that he can be a serious player at work and an engaged father."

She says fathers need to step and make their caring responsibility visible to others, which will also help women.

Ms Broderick points out that just as women and men returning to work after parental leave face practical and financial challenges, so do some employers and especially small businesses.

The Human Rights Commission has launched a research project into the issue of pregnancy discrimination. It is expected to report back early next year.