Swiss expatriate Juerg Buergin, 41, is contesting charges filed against him and 50 other local and foreign men accused of paying for sex with the 17-year-old call girl in 2010 and 2011, a case involving prominent figures that caused a scandal in Singapore.
"The prostitute, in a conspiracy with the pimp, had deceived the accused as to her true age and thereby intentionally induced him to engage her services," his lawyer Selva Naidu said in a written statement released to journalists.
The prosecution said the website advertised the girl as an "18-year-old polytechnic student".
Buergin's lawyer said the prostitute had not been "coerced into the trade by threats or intimidation".
Singapore law makes it illegal for anyone to pay for the sexual services of a girl under the age of 18.
The offence is punishable by up to seven years in prison, a fine, or both.
Buergin, who is married, is out on bail.
Prosecutors said Tuesday that he booked the prostitute, who went by the name "Chantelle" on the escort agency website, on two occasions in September 2010 and January 2011 and met her at a luxury hotel.
The case caused an uproar last year after 51 men, including business executives, a former school principal, a navy captain and a police superintendent were accused of paying for sex with the girl.
One of them was socialite and environmental activist Howard Shaw, 41, a grandson of Asian movie mogul Runme Shaw.
He was sentenced to 12 weeks in jail but released after eight weeks for good behaviour.
The Straits Times said 18 men have so far been convicted in connection with the case, with Buergin the first to go on full trial after contesting the charges.