Former world number one Andy Murray said the difference in prize money at the Dubai Championships is a "big step backwards", with the men's singles winner set to receive five times more the amount as compared to the women's champion.
Latvia's Jelena Ostapenko took home $154,000 after winning the women's WTA 500 event by beating Veronika Kudermetova in the final last weekend.
The men's ATP 500 event, which ends this weekend, will result in the winner receiving prize money worth $773,000.
"Obviously that's a big step backwards, so it's not great," Murray said after his 7-5 6-2 loss to Jannik Sinner.
"Obviously if they're the same size events one week apart, that's quite a big discrepancy."
Tennis is usually considered the leader in the battle for equality for women's sport, with equal prize money paid to men and women at the four Grand Slams.
"There has been tournaments on the tour, like the Washington event, for example, with the different size events, the prize monies are different," Murray added.
"I've also played the tournament in Brisbane for the men, which is a smaller event compared to women, and the prize money is flipped the other way."