Julie Bishop has defended her comment that women can't have it all, saying it has sparked a healthy debate that should encourage flexibility in workplaces.

The deputy leader of the opposition made the comment on Sky News on the weekend, and repeated the sentiment on ABC radio on Monday, saying she'd since received refreshing tweets from her supporters.

"I'm not suggesting for a moment that people, men or women, can't find balance in their lives," she said.

"I'm just stating a fact. In striking a balance there are trade-offs between the time you spend with your family and the time you spend at work or pursuing your career.

"I think it's healthy that we talk about this and it does focus on what we need to achieve in our workplaces."

The belief that modern women could have it all was a myth, she said.

"I don't know that women really do believe that they can have it all - they might want to say it.

"If you're spending time at work, you're not spending time on other things."

Ms Bishop cited Australia's first female attorney-general Nicola Roxon as an example of someone whose work impinged on her personal life.

"Just 12 months into it, she has announced her retirement as she felt unable to effectively balance the dual responsibilities she had as a politician and as a mother," she said.

"There are some real challenges in work-life at present and of course, we need to support young women who are aspiring to combine it all, but they have to understand that you will make a sacrifice."