SEOUL (REUTERS) - South Korea wants to root out age-old prejudices against single parents and unmarried couples who live together, encouraging more people to have children in the battle against its stubbornly low birth rate and rapidly ageing population.

The social pressure has proved a drag on a birth rate that ranks the lowest among rich nations, and coupled with a sluggish economy, has helped make first-time South Korean mothers the world's oldest.

As policymakers scramble to avoid the complications a dwindling population has brought to neighbouring Japan, South Korea's Finance Ministry is taking aim against social and regulatory prejudice in its economic policy plan for next year.

"We plan to change the social perception on various family forms to boost the birth rate," the ministry said in a statement released on Wednesday (Dec 16), although it did not give details.

"We want to expand support for single mothers and also launch campaigns that will change people's perceptions of couples living together," said a Finance Ministry official who declined to be named as he was not authorised to speak to media.

South Korea's birth rate of 1.205 children per woman is the lowest among the rich nations of the OECD grouping, where it is also ageing the fastest. Its working age population will start shrinking in 2017.

Young people are compelled to delay marriage and having children by a sluggish economy that has pushed up youth unemployment. A shortage of daycare and the high cost of raising and educating children are other deterrents.

The average age of first-time South Korean mothers is the world's highest, at 30.7 years, says Statistics Korea.

It will be tough to alter attitudes in a country where young couples living together before marriage is almost unheard of, and where just 1.9 per cent of children are born out of wedlock.

That compares with Sweden, where unwed mothers accounted for 54.4 per cent of births in 2013, and the birth rate is 1.89 per cent.

Penalties for single parents

Job-seekers in South Korea are often asked their family status, which can penalise single parents, and children of single parents are often stigmatised, even into adulthood.

Single parents living alone with children pay higher taxes than married couples with children and a similar income.

"It is especially difficult for female single parents to find work because of gender discrimination in employment," said Ms Park Yeong Mi of the Korea Unwed Mothers Support Network.

"Single mothers are seen as unchaste, as not conforming to social norms. Single fathers are viewed with even more social stigma, because of the patriarchal culture."

Several government departments will collaborate in the effort to change the outlook on marriage, although detailed plans are few, the Finance Ministry official said.

"We still have to feel out what to do specifically, and our circumstances won't turn into what you see in countries like France, but if there is prejudice in regulations, we will work to ease them."

A committee chaired by President Park Geun Hye released a blueprint to tackle the population crunch and said last week it planned to raise acceptance of "various forms of family", including teenage parents.