South Korea's health ministry is turning off the lights in its offices once a month to encourage staff to go home early and make more babies.

The ministry is charged with boosting the nation's low birth rate, which is one of the world's lowest.

The ministry said the lights will be turned off at 7.30pm every third Wednesday in the month to 'help staff get dedicated to childbirth and upbringing'.

Those with urgent duties will be exempt from the switch-off.

'Going home early may have no direct link to having more kids, but you cannot just completely rule out a possible link between them,' said Choi Jin-Sun, who is in charge of the project at the ministry.

South Korea's birth rate remained near the world's lowest at 1.19 in 2008 and there are fears the population will begin shrinking within a decade.

'It won't be too long before our children are burdened with supporting the elderly,' Health Minister Jeon Jae-Hee told the Korea Times newspaper.

'Korea may lose out in the global economic competition due to a lack of manpower. It is actually the most urgent and important issue the country is facing.'

Married staff at the ministry are not doing their bit, with an average of 1.63 children compared to the average of 1.82 among all civil servants. The ministry aims to increase the figure to 2.0 in two years.

The ministry has various incentives, including cash gifts for staff who produce more than two babies.