Ms Sutherland, a partner of 15 years at Herbert Smith Freehills, said she received a pay rise after speaking up.

"When I saw that there were partners made at the same time as me doing better in remuneration terms, I would just raise it and ask what else do I need to do to achieve that," she said.

New research has found that young Australian women are just as successful as their male peers at asking for and negotiating a pay rise.

But older women who ask for wage rises as often as men are 25 per cent less likely than men to get a raise when they ask.

And as few as one in five women are in the top 10 per cent of earners in Australia.

The findings come from two new international studies using Australian data and research.

Ms Sutherland said it was good news younger women were having greater success in negotiating a pay rise.

But new research suggests that older women may need more support and protection from unconscious bias in favour of younger people entering the workforce.

"I think the most important thing is having the confidence to ask what is expected of you in your role and how your peers are ranked and how you are ranked in relative terms," Ms Sutherland said.

"Historically it's been hard to ask those questions. But here we are encouraging people to speak up and ask for information."

An international study by Sarah Voitchovsky from the University of Melbourne and researchers from the London School of Economics and the Bocconi University in Milan shows that of the top 10 per cent of earners in Australia, only one in five to one in three are women. Of the top one per cent of earners, between 14 and 22 per cent are women.

The study Top incomes and the gender divide found the proportion of women in the top 10 per cent ranged from 21.5 per cent in Norway and 25.4 per cent in Australia to 32.6 per cent in Spain.

"Differences across countries are stronger, but still relatively small, when we look at the proportion of women in the top 1 per cent of the income distribution: it lay between 14 per cent in Norway and 22 per cent in Australia, Canada and Spain," the researchers said.

"The second striking feature – and one that we did expect – is the decline in the proportion of women as one rises higher on the income scale.

"The share of women in the top 10 per cent is between 1.4 and 1.9 times the share of women in the top 1 per cent, except in Australia."

Ms Voitchovsky said that "in the old days, the rich were those with property; they have been replaced by CEOs and entrepreneurs, among whom women are less well represented".

The proportion of women at the top has generally increased over time but less in the upper ranges.

"In other words, women now make up more of the top 1 per cent, but they still are a distinct minority and they become rarer the higher one climbs," she said.

"Earnings represent an important source of income for people at the top of the distribution and trends in the labour market are obviously part of the story.

Another study by researchers at Cass Business School, the University of Warwick and the University of Wisconsin, shows that women ask for wage rises just as often as men, but men are 25 per cent more likely to get a raise when they ask.

The study titled, Do Women Ask?, found no evidence for the assumption that women are less pushy than men or that they hold back to avoid upsetting their boss.

The researchers from the University of Warwick, the University of Wisconsin et al studied a randomly chosen group of 4,600 workers across more than 800 employers to test the assumption that women get paid less because they are not as pushy as men.

Co-author Andrew Oswald, Professor of Economics and Behavioural Science at the University of Warwick said the study suggested "there is some element of pure discrimination against women".

The research uses data gathered in the Australian Workplace Relations Survey which covers the period 2013-14 which is a representative sample of Australian employees and workplaces.

The researchers said young Australian women are negotiating their pay and conditions more successfully than older females, "and perhaps that will continue as they become more senior".

Marian Baird,  Professor of Gender and Employment Relations from the University of Sydney said: "The results seem to support the conclusion that many of us have also suspected, that is, that there is outright pay discrimination against women in some instances".

"This might be built on unspoken and implicit biases about men having the right to earn more than women.

"The conclusions also show that women more often work in jobs that don't provide the opportunity to negotiate their own pay - and this is a result of occupational segregation in the labour market."

Libby Lyons, Director Workplace Gender Equality Agency said previous studies have shown that women have less successful outcomes than men in pay negotiations.

"This new research suggests women's appetite for negotiation is no different from men's," she said.

"Gender bias often underpins promotion, performance and pay decisions," she said. "For example, a perception that men are the family breadwinner and more deserving of a pay rise can influence pay decisions."