Australia's first study of how sexual orientation affects wages has revealed gay men get paid up to 18 per cent less than their straight counterparts.

The paper's author, University of Melbourne economist Andrea La Nauze, says the only apparent explanation for the "substantial wage penalty" suffered by gay men is prejudice.

"The main take-home message from the paper is that Australian workers doing the same job seem to be paid differently because of their sexual preference," she said.

The findings are consistent with studies in Europe and the US which have also identified a "robust and persistent" wage penalty for gay men.

"There are grounds for concern that workers in Australia, particularly gay men, are discriminated against because of their sexual orientation," Ms La Nauze's paper concludes.

The wage disparity between gay and straight men identified by Ms La Nauze's modelling is strikingly similar to the gender wage gap – the long standing gulf between average full-time earnings of men and women. Wages data released on Thursday showed the gender pay gap in Australia has reached a record 18.8 per cent. On average, a man working full-time earns nearly $300 a week more than a female full-timer.

However, Ms La Nauze found the negative pay gap experienced by gay men relative to heterosexual men does not apply to gay women. Instead gay women enjoy a wage premium of up to 13 per cent compared with heterosexual women. Ms La Nauze says one possible explanation is that gay women are rewarded because their employers have a perception that they are less likely to leave the workforce to have children than heterosexual women.

"If employers believe heterosexual women are more likely to have children, or are more likely to take on a higher proportion of child-rearing duties, and if employers believe this results in lower productivity, then heterosexual women may be penalised and receive lower wages than lesbian women," she said.

Overseas studies in other have also identified a modest wage premium for gay women.

Ms La Nauze used data from the Household Income and Labour Dynamics in Australia (HILDA) survey to compare the wages of heterosexual and gay workers between 2001 and 2010, taking into account factors like occupation and levels of education. The analysis showed men in same-sex relationships experience a negative wage premium of between 8 per cent and 18 per cent depending on the model. Women in same sex relationships earn a positive wage premium of between 0 per cent and 13 per cent.

"I sincerely hope that we do not live in a society that pays someone less for the same job because of their sexual preference," Ms La Nauze said. "I hope that the next paper I see on the issue finds that gay men do not face a wage penalty."

Discrimination on the basis of sexual orientation is unlawful in Australia but La Nauze says improved enforcement of existing anti-discrimination laws may be required to remedy the wage gaps she identifies. Better education and even targeted "incentive mechanisms" may also help.

"We should devote effort to finding out why differences in wages exist, whether there is direct or indirect discrimination along lines of sexual orientation and if so what can be done about it," she said.

The study titled Sexual orientation–based wage gaps in Australia: The potential role of discrimination and personality is published in the The Economic and Labour Relations Review.