Defending champion Venus Williams has spoken of her disappointment at the gap in prize money for men and women on day one of the Wimbledon Championships.
Venus Williams is defending her third Wimbledon title
Writing in the Times, she said the £30,000 pay difference between men's and women's singles winners sends out a message that women are inferior.
Some argue that men deserve more because they play up to five sets while women play up to three.
The All England Club said this year's prize money would not be changed.
The women's singles winner will get £625,000 compared to £655,000 for the men's champion. All other major international tennis tournaments offer equal pay.
In the article, Ms Williams wrote: "I'm disappointed not for myself but for all of my fellow women players who have struggled so hard to get here and who, just like the men, give their all on the courts of SW19.
"I'm disappointed for the great legends of the game, such as Billie Jean King, Martina Navratilova and Chris Evert, who have never stopped fighting for equality.
"And disappointed that the home of tennis is sending a message to women across the world that we are inferior."
Last week culture secretary Tessa Jowell wrote to tournament organisers, the All England Club, expressing deep concern at the inequality.
In response, the All England Club said prizes were fixed each year and the club would not change its stance.
It said its financial policy was based on simple economic reality, not sexism.
But the Lawn Tennis Association's new chief executive Roger Draper gave his public backing to equal pay.
Mr Draper is one of seven LTA members on the Championships committee, who sit alongside 12 All England Club members.
He said "Tennis needs to be a modern sport and one which reflects the wider world.
"My vote on the Championships committee will continue to be for equality of pay.
"The LTA jointly host these Championships and we will continue to lobby and work with the All England Club to ensure that in future years there is parity."