Japanese tennis superstar Naomi Osaka Saturday slammed "ignorant" remarks from the Tokyo Olympics' chief organiser after a sexism row that has triggered an angry backlash and calls for his resignation.

Osaka, a leading face of the Games in her home nation, joined growing criticism of former Japanese prime minister Yoshiro Mori, 83, after he complained that women speak for too long in meetings.

The gaffe-prone Mori has apologised but refused to step down, and attempted to justify his comments by explaining he doesn't "speak to women much".

"I feel like that was a really ignorant statement to make," said Osaka, 23, referring to the original remarks.

"I think that someone that makes comments like that, they need to have more knowledge on the thing that they're talking about."

Osaka, the world's top-earning female athlete, emerged as a potent voice on social issues last year when she wore facemasks highlighting victims of racism and police brutality at the US Open.

"I also want to hear the reasoning behind those comments," said the three-time Grand Slam winner, ahead of the Australian Open in Melbourne, a tournament she won in 2019.  

"I also want to hear the perspective of everyone else that surrounds him."

Olympic medallists, Japanese sports officials and Games volunteers have lined up to lambast Mori, while Tokyo's governor said she was left "speechless" by the remarks.

Japan's Asahi Shimbun daily called in an editorial for Mori's resignation, and an online campaign urging his sacking has attracted more than 108,000 signatures, including from Grammy-winning musician Ryuichi Sakamoto.

The Mainichi Shimbun on Saturday reported that Mori had considered quitting in the wake of the criticism, but was talked out of it.

"From the beginning, I don't have no regrets about the chairmanship," Mori told the daily. 

"I had once decided to resign, but I held back after being strongly convinced" by Tokyo 2020 officials, he added.

What he said wasn't right

Despite the uproar, the International Olympic Committee said Thursday it considered the issue "closed" after Mori's apology.

Osaka stopped short of calling for his resignation, but said he should be made to understand why he has caused so much offence.

"I'm not sure if it's a situation where someone should demand that he resigns or if it's just something that people need to make him understand that what he said wasn't right," she said. 

Mori is also a former president of the Japan Rugby Football Union, and JRFU board member Yuko Inazawa told Japanese media on Friday she believed his comments were aimed at her.

Japan ranks highly on a range of international indicators, but persistently trails on promoting gender equality -- coming 121 out of 153 nations surveyed in the World Economic Forum's 2020 global gender gap report.

The row is the latest headache for organisers already battling public disquiet about the postponed Games, with polls showing more than 80 percent of Japanese oppose holding the event this summer with the coronavirus pandemic still raging.

Mori, who has a history of controversial remarks, had already attracted criticism earlier in the week by insisting the Games would happen "however the coronavirus (pandemic) evolves".

Osaka said she remained keen to compete at the Games, which start in July, but added that public approval was crucial for them to go ahead.