Former Swiss banker Juerg Buergin has launched an appeal against his conviction for having sex with the underage prostitute at the centre of the vice ring case.

The 41-year-old was sentenced to four months and three weeks in prison last month after being found guilty of paying the 17-year-old for her sexual services. Eighteen other men have received jail terms of between eight and 16 weeks for having sex with the same social escort.

Buergin's lawyer, Mr Selva K. Naidu, said the petition of appeal was filed yesterday.

He told The Straits Times it would be based on the issue of mens rea, or "guilty mind".

During the trial, Buergin claimed he did not know the victim was under 18 - the legal age of consent for prostitutes in Singapore.

But in his grounds of decision, District Judge Eddy Tham found the law did not require him to have mens rea - knowledge of the girl's age - in order to be found guilty.

No date has been fixed for the appeal hearing.

Buergin, a father of two who is now in Admiralty West Prison, was the first to go on trial in the online vice ring case involving 51 men. All of them are said to have had sex with the same girl. Two men have pleaded not guilty and their cases are ongoing.

MARYAM MOKHTAR