The idea dates back hundreds of years, when churches and monasteries all over Catholic Europe had similar boxes.

Pastor Lee Jong-rak said, "I've never encountered a mother who abandoned her baby if she had the means to support the child. This is the last place mothers come to after looking for every other option to raise their baby."

As of Wednesday 1,515 babies had been abandoned in the box. Around 1,000 came with a letter from the mother saying she was sorry.

A "baby box" at Joosarang Church in southern Seoul where destitute mothers can place their baby and ring a bell to alert staff marks its 10th anniversary this year.

When the church first set up the box, it was accused of encouraging mothers to abandon their babies. The Ministry of Health and Welfare and the district office demanded that the church take it down since mothers who leave their babies there can be charged with abandonment. There were also phone calls from incensed citizens.

But Lee stuck to his guns, telling critics that destitute mothers will continue to abandon their babies without the box, and that would be worse. He also refused to install security cameras that could provide evidence to prosecute them and regularly cleaned up fingerprints left on the box.

Every effort is made to dissuade the mothers. An alarm goes off each time a baby is placed in the box, prompting the pastor or volunteers to rush outside to see if they can reason with the destitute mothers, offering financial assistance.

Some 30 percent of the mothers who leave their babies end up deciding to continue caring for them, according to the church. Many are teenagers and often give birth secretly in public toilets or friends' homes.

The babies who are left are cared for by Lee and four volunteers for about a month and then sent to orphanages. The volunteers are instructed not to hold the babies too often lest they grow too attached to them. Seo Si-on, a volunteer at the church, said, "We don't want the babies to get hurt if they lose the love and attention once they're sent to an orphanage or foster home."

Lee started operating the box with his own money, but a decade on he has 1,300 sponsors who send between W10,000 and W20,000 a month or donate baby formula and diapers (US$1=W1,120).

For the last four or five years the government has stopped demanding the church shut the baby box down. "I want to protect the babies, and the box will disappear only once society is willing to accept single mothers."

A law allowing single mothers to keep newborn babies off their or the father's family records is currently awaiting National Assembly approval to prevent discrimination due to their illegitimate birth.