Regulations are failing to stop illegal ivory being sold in the Netherlands, citizens’ network Avaaz has said after carrying out a market test.

The organisation successfully offered 18 antiques for sale in antique shops and on Marktplaats, despite not providing certificates of origin. Under international rules ivory acquired from animals after 1990 is banned from sale, while objects that originate between 1947 and 1990 can only be sold with a certificate.

Carbon dating testing by the University of Oxford showed that 13 of the 18 objects contained ivory that originated later than 1947. According to Avaaz, its test proves that the rules were too easily circumvented by illicit traders.

Marktplaats rules state that any ivory offered for sale must either carry a certificate or a statement that predates the 1947 threshold. But the website admitted that it is difficult to verify the age of an item.

The Dutch Food and Consumer Product Agency (NVWA) is responsible for enforcing the international CITES rules, which are designed to protect 5000 endangered animal species and 30,000 species of plant. On average inspectors investigate 10 cases a year, most of which concern ivory.