TOKYO (REUTERS) - Japan must put more women in key posts to boost its economy and to prove its ruling party has changed its hidebound ways, the party's top spokeswoman said on Tuesday, just days after two female party executives clashed over quotas for women managers.

"To mobilize women would create a breakthrough in Japan's economy. This itself would change the paradigm of Japan's economy and ought to be ensconced as part of our growth strategy," said Yuriko Koike, a multilingual former defence minister who was appointed head of the LDP's public relations headquarters after the party surged back to power last month.

Mr Shinzo Abe, who returned to the premiership in December after the LDP's stunning election victory, three years after it was ousted, has appointed Ms Koike and two other women to important party posts in what the prime minister called an effort to show that the long-dominant party has changed.

But in a sign the conservative party remains ambivalent about the role of women, the two other female appointees - LDP policy chief Sanae Takaichi and party General Council Chairwoman Seiko Noda - quibbled on Sunday over the need to set a legally binding target for boosting women's share of managerial posts in the public and private sectors to more than 30 percent by 2020.

The LDP's campaign platform called for a numerical target but did not specify whether it would be compulsory.

Ms Takaichi, a staunch conservative on social issues, raised the concern that a quota would lead to "reverse discrimination", while Ms Noda backed the measure as necessary to spark change, according to reports of their exchange on a television talk show.

"Ten years ago, I felt the same (as Takaichi) but recently I realised if we don't do this, nothing will change," Koike told Reuters in an interview at a bustling LDP headquarters.

The International Monetary Fund (IMF) urged Japan in a report in October to make better use of working women, noting females accounted for 9 percent of the country's managers as of 2009, compared with 43 percent in the United States. Female labour force participation overall also lags other advanced countries.

Among the barriers cited by experts are corporate hiring practices that shunt women to non-career-track jobs, a tax code that favours housewives and the tendency of many women to drop out of the workforce after childbirth, due partly to social pressure but also to a shortage of childcare facilities.