South Korean President Moon Jae-in, who promised to be a "feminist leader" during his election campaign, was under fire Thursday for sending condolence flowers to the funeral of a convicted sex offender's mother.

Moon and dozens of senior politicians -- almost all of them male, and from both sides of the aisle, but mostly from his ruling centre-left Democratic Party -- sent bouquets for this week's ceremony for Ahn Hee-jung's mother.

Former provincial governor Ahn was once a rising star and came second to Moon in the race for the 2017 Democratic presidential nomination, but was convicted last year of sexual intercourse by abuse of authority after his female assistant accused him of repeatedly raping her.

He is serving three and a half years in prison.

The controversy over the funeral laid bare the attitudinal gender divide in a society that remains highly patriarchal -- it has the highest gender wage gap in the OECD club of developed economies.

And women hold only 19 percent of seats in its newly elected parliament, which would put it 116th in the Inter-Parliamentary Union's previously published 2020 ranking.

Sexual harassment victims often face pressure to stay silent for fear of public shaming, but signs of change emerged after the country's own #MeToo movement -- sparked in 2018 by a prosecutor who publicly accused a superior of groping her at a funeral, prompting many to share their stories.

Ahn was by far the highest-profile individual named as a result.

But after he was temporarily released from jail to attend the funeral ceremonies, he received visits from scores of political heavyweights offering their condolences -- among them Prime Minister Chung Sye-kyun, his predecessor Lee Nak-yon, and ruling party leader Lee Hae-chan.

Ahn allowed media to cover the event and pictures showed a large white wreath in prime position, with a plaque bearing the presidential logo and Moon's name.

- Furious response -
Women's groups and progressive politicians reacted furiously, saying the moves demonstrated the political establishment's traditionalist mindset and sent a signal that sexual crimes could be disregarded.

"Every message from a president is an act of governance, including condolences," wrote commentator Choi Moon-sun in the Hankook Ilbo newspaper.

When Moon sent the flowers, she said, "there was no president for South Korean women".

Jo Hye-min, a spokeswoman for the opposition Justice Party, said Ahn's victim was "still struggling in life in the face of non-stop shaming".

"It is so clear that a message and action by a politician is not a personal one but has a public nature," she said. "We can't help but ask what their actions mean."

The presidential office said Thursday it sent the flowers following a "comprehensive review of the situation".

Ahn was due to return to prison Thursday.