The number of child sex workers in Indonesia has more than doubled in the past decade, with the majority operating around resorts amid the country's booming tourism industry, an NGO has warned.

Jakarta, Bali, Batam, Lombok - the country's main tourist destinations - are among the locations with the highest prevalence of child sex workers, added the Indonesian branch of the NGO, End Child Prostitution in Asian Tourism (ECPAT).

It said other hubs for child sex workers include Pontianak in West Kalimantan, Riau Islands' Tanjung Balai Karimun and Papua's Mimika.

The ECPAT survey found that 80 per cent of the children were employed for sex at recreational sites across the country, while the rest were stationed at mining sites, military barracks and rest areas for drivers.

"The figure has more than doubled in just 10 years. I am afraid it will continue to grow alongside the development of the tourism industry," local ECPAT coordinator Ahmad Sofyan said.

He attributed the twofold rise in child sex workers to the growing tourism industry.

Sofyan said most child sex workers were girls aged between 14 and 15, originating from West Java areas like Indramayu and Sukabumi.

Contrary to popular belief, not all were roped into the sex industry via human trafficking but instead sought out work themselves, he said.

Eradicating this illegal practice has proven difficult as many people consider having sex with a minor perfectly legitimate, as long as the child consented to the act.

Tight business competition and a lack of regulations also hampered attempts to fight the child sex industry, he added.

"We have no specific regulations to address this issue. It is not covered under the 2002 Law on Child Protection," Sofyan told The Jakarta Post after a meeting Thursday between the government and tourism stakeholders to discuss the growing problem.

He said law enforcers were still divided over the term "sexual exploitation", which as an act is banned under the 2002 Law on Child Protection.

Firmansyah Rahim, the Culture and Tourism Ministry director general for tourist destination development, admitted there were no specific regulations addressing child sex tourism, causing difficulties on the part of law enforcers to combat the practice.

He told the meeting the government is proposing the tourism industry be obliged to abide by "religious principles" and ban gambling and sex tourism in their resorts.

The proposal has been included in a new bill, currently being deliberated at the House of Representatives, to revise the 1990 Law on Tourism, Firmansyah added.

Comr. Murnila from the Jakarta Police's women and children services unit said her office found it difficult to nab employers of child sex workers as they often hid the children or lied about their real ages during raids.

The police can only handle cases involving children forcibly recruited into the sex industry through trafficking and not those working at their own free will, she said.

Murnila said about 30 per cent of sex workers in the country were males and females under the age of 18, and that police raids often netted children aged as young as 11 and 12.