TOKYO (AFP) - A Tokyo city lawmaker from Japanese Prime Minister Shinzo Abe's ruling party admitted on Monday he had been responsible for a sexist taunt shouted at a young assemblywoman in a debate on motherhood.

In a case that has cast a harsh spotlight on the attitudes of many of the older men who occupy senior positions in Japanese public life, 51-year-old Akihiro Suzuki said he had yelled: "Why don't you get married?" at the opposition assemblywoman.

The episode, which took place last Wednesday, has undermined Mr Abe's repeated appeals for Japan to boost the role of its under-employed women and encourage them into more senior positions. Mr Suzuki had previously repeatedly denied shouting the taunt.

"I made the comment out of my feeling that I would like her to get married soon, as we see the issue of a shrinking population and an increasing number of women not marrying until late," Mr Suzuki told a hastily-arranged press conference.

"It was such an inconsiderate remark to those who cannot get married even if they wish to," said Mr Suzuki, himself married with three children.

The object of his jeering was Ayaka Shiomura, 35, who was questioning senior figures in the Tokyo city administration on plans to help current and future mothers when abuse erupted from seats occupied by Liberal Democratic Party members.

Mr Suzuki's shout was captured on tape, while some of those in the chamber said they had also heard laughter and taunts such as "Are you not able to have a baby?" Despite the apparent presence of numerous reporters, the story initially only appeared in two liberal-leaning newspapers last Thursday, but gathered pace both domestically and internationally.

By Friday, it had become a major theme and dominated weekend television talk shows, resulting in Mr Suzuki admitting his part on Monday and apologising to Ms Shiomura in a room full of journalists. He resigned his party membership, but insisted he would stay on as an assemblyman.

While the mea culpa extracted from Mr Suzuki has taken some of the sting out of the issue, there will doubtless be calls for more heads to roll, with commentators on his Facebook page pointing out he was not alone.

"Apparently it wasn't only this man, because there seemed to be some others who made the 'Can't you have a baby?' comment," wrote Yumi Tsuchihashi.

Ms Shiomura is set to meet foreign press in Tokyo on Tuesday, further fuelling the debate.

Japan has one of the lowest rates of female workforce participation in the developed world, and most economists agree it badly needs to boost the number of working women. But a lack of childcare facilities, poor career support and deeply entrenched sexism are blamed for keeping women at home.