IMMIGRATION authorities are launching a crackdown on 'marriages of convenience' arranged by crime gangs to import prostitutes from Southeast Asia. Authorities aim to tackle a rise in bogus marriages between women seeking work in Hong Kong brothels or bars and local men being paid up to $30,000 to sponsor them as brides. The most blatant case uncovered involved one 'husband' who sponsored four Filipino women as his 'wives' in December. Most sex workers entering fake marriages are from the Philippines, but others arrive from Thailand or Malaysia, immigration officers said. The prostitutes generally stay two or three months while their immigration applications are processed, but can earn up to $300,000 during that time. Some stay for longer periods. Many meet their 'husbands' just once and go to immigration offices posing as couples who have fallen in love at first sight and married hurriedly. 'Girls can earn money in a few weeks; the 'marriage' is just an easy way to get in here,' said assistant principal immigration officer Tony Law Yiu-tung. 'The trend has been increasing but we are taking action. We imposed tightened measures in examining and processing these applications.' Police trying to clamp down on prostitution have urged the Immigration Department to take action against the rackets. Mongkok district Chief Superintendent Stuart Wringe said Thai women working in vice dens often entered the territory in this way. Immigration officers who suspect a bogus marriage can question couples about their relationship, families and living arrangements and even visit their home - tactics adopted by American officials in the film Green Card. The Security Branch is considering a proposal to stop the practice of allowing visitors to remain in Hong Kong while their applications for a change of status are processed. If it wins approval, people will have to apply for work and dependent visas through British embassies overseas before arriving. A total of 1,767 applications have been made from Southeast Asian women to join their husbands over the past 23 months, of which 446 were refused. Although most of the fake spouses are Filipino and Thai women driven to prostitution by poor living conditions at home, men from India and Pakistan have also been entering marriages of convenience to seek better-paying jobs in Hong Kong.