A BBC Sport study reveals 30% of sports - including golf, cricket and squash - pay prize money that rewards men more highly than women.
The biggest disparity appears to be in football where Arsenal won both the men's and women's FA Cup this year, but while the men were given £1.8 million, Arsenal Ladies received £5,000 for their win.
Tennis is one of 25 sports where men and women receive equal prize money, and WTA chief executive Stacey Allaster says "it does not make any sense" that top female athletes in other sports are missing out on a greater share of sponsorship money and media exposure.
Katie Gornall reports.
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