A South Korean ministry is offering cash rewards to companies whose employees promise to stay away from prostitutes after year-end parties.

The Gender Equality Ministry is inviting employees to register on its website under their company name and persuade as many colleagues as possible to sign a pledge not to buy sex.

The company with the most names will receive one million won (about R7000).

So far more than 1200 companies have signed up for the campaign which began on December 6, with the top one gathering about 1060 pledges, the ministry said.

"We are receiving a good response from many people despite criticism of our campaign aimed at eradicating prostitution," a ministry official said on condition of anonymity.

"The idea is based on a survey of our corporate culture, that many men visit prostitutes or accept sex as a ritual after drinking heavily at year-end parties."

The campaign, which the ministry said is aimed at eradicating a culture of male exploitation, has been derided by critics.

"This is a naive way of thinking. The ministry is wasting taxpayers' money on ineffective measures. Moreover, the ministry regards all men as potential clients of prostitutes," the JoongAng Ilbo newspaper said in an editorial.

The government has maintained a "zero-tolerance" policy on the sex industry since a tough anti-prostitution law took effect in 2004.

Brothel owners face up to 10 years in jail or 100 million won in fines, while buying sex is punishable by up to one year in jail and thee million won in fines.

Official data shows about 330,000 women are engaged in the sex industry. - Sapa-AFP