The Thai government today imposed a nationwide ban on the castration of young boys seeking to join the country's thousands of ladyboys.

Fearful that the operations could cause severe damage to both their mental and physical health the Public Health Ministry issued a ministerial order conveyed to all the country's hospitals and private clinics.

"As of today, doctors can perform the surgery if there is a medical reason to do so - not for any other reason," ministry spokesman Suphan Srithamma said.

The move follows reports that boys as young as 11 and 12 have been queuing for the operations - the first stage in a complete sex change operation.

Young boys believe the operation will help them develop with more feminine complexions as they grow older.

Operations have been banned on all youths aged under 18 whether they have parental consent or not.

Thousands of ladyboys are employed in Thailand's sex industry. Ladyboy bars and clubs have increased significantly over the last five years and seem popular with foreign tourists.

Last week the Medical Council of Thailand warned of the health risks associated with castration, which could damage hormone growth and physical development.

Natee Teerarojjanapongs, the leader of the Gay Political Group of Thailand, also called for action to be taken against clinics performing castrations on young ladyboys.

"It's a totally wrong perception that castration will make boys more feminine," Natee told The Bangkok Post.

"These youngsters should wait until they are mature enough to thoroughly consider the pros and cons of such an operation."

One clinic in Bangkok alone has carried out 500 castrations in the last four years.

Doctors who flout the law face imprisonment or a fine or both.