Female world leaders have been known to vent about double standards in politics during informal bathroom meetings on the sidelines of major global summits, former prime minister Julia Gillard says.

Ms Gillard, who was Australia's first female prime minister and is now the chair of the Global Partnership for Education, said the world's most powerful women "all had some complaints over the washbasin" when they got together.

"There were very few women at the G20 ... And at those meetings, you would, I mean, often on a trek to the bathroom, or at the hand basins in the bathroom, talk to each other, and have a wry smile about some of the ridiculous things that get written about you," Ms Gillard told BBC radio.

She praised German Chancellor Angela Merkel for doing a "clever thing" by effectively adopting a uniform to avoid a focus on her clothing.