Japan's popular environment minister said he will take paternity leave when his first child is born later this month to be a good example for working fathers in Japan, where men are largely absent from child-rearing.

Environment Minister Shinjiro Koizumi said on Wednesday he will take two weeks of leave over three months on the condition it would not affect his parliamentary and Cabinet duties.

With Japan facing an ageing population and a dwindling birthrate, the government recently began promoting paternity leave.

More:

Last month, it adopted a policy allowing male public servants to take more than a month of leave with the birth of a child.

While the governors in Hiroshima and Mie in western Japan have taken paternity leave, Koizumi is the first Cabinet minister to do so.

The 38-year-old politician said it was a difficult decision, but that he was going ahead with the plan to pave the way for other male employees in his ministry and working fathers elsewhere.

Koizumi is the son of maverick former Prime Minister Junichiro Koizumi and is considered a future prime ministerial hopeful.

"Honestly, I had to think over and over how I should take time off for child-rearing, or take paternity leave while fulfilling my public duty as environment minister, " Koizumi told a group of ministry officials and reporters.

"Unless we change the atmosphere, government employees presumably won't start taking paternity leave."

Chief Cabinet Secretary Yoshihide Suga told reporters that he hoped Koizumi's decision would have a positive effect on attitudes to male parenting.

There are no official records on whether cabinet ministers have previously taken parental leave, but Koizumi is the first to publicly announce he is doing so.

'Pata-hara'

Japan has relatively generous parental leave policies, allowing men and women partially paid leave of up to 12 months.

While recent surveys show a majority of eligible male employees hope to take paternity leave in the future, changes are coming slowly and few fathers of newborns take time off due to the intense pressure to focus on work.

Only 6 percent of eligible working fathers took paternity leave in 2018, according to the Ministry of Health, Labour and Welfare, far short of the government's modest 13 percent target for 2020.

Many working fathers fear taking paternity leave will damage their careers, and those hoping to take leave often face warnings from their bosses or colleagues.

A handful of men have sued their employers alleging they were subject to what is known in Japan as "pata-hara", short for paternity harassment, after taking parental leave.

Koizumi is the son of maverick former Prime Minister Junichiro Koizumi and is considered a future prime ministerial hopeful [Jiji Press via AFP ]

The issue is a particular concern given Japan's birthrate, which in 2018 was one of the world's lowest - and far below the rate the country needs to maintain its population.

Koizumi said he hopes to inspire further debate over how to balance work and family duties, including child and elderly care, in a sustainable way.

"I hope there will be a day when lawmakers' paternity leave is no longer news, " he said.

He expressed his intention last year to take paternity leave when he announced his marriage to former newscaster Christel Takigawa.

He has since faced divided public opinion, including criticism that he should prioritise his duties as a government minister.

Koizumi's announcement received a mixed reaction on social media. Some people said two weeks of paternity leave was a marginal amount and that he may be only trying to get attention, but many welcomed his decision in the hope that it would bring about some change.

Shintaro Yamaguchi, a University of Tokyo professor and expert on labour economics and parental leave policies, said that even short-term paternity leave can make a difference, citing studies abroad.

"Paternity leave taken by leaders seems to have a big influence on people around them, " he tweeted.