Dutch food and product safety inspectors have tracked down almost 500 illegal and unlicenced tattoo artists over the past four years, according to figures published on Wednesday.

It has been illegal to tattoo people in the Netherlands without proper papers since 2007. Around 10% of the parlours visited by the NVWA’s inspectors between 2011 and 2014 were found to be operating without a licence.

The rules, which cover hygiene, safety and the quality of the ink, were tightened up in 2012.

Tattoos and piercings are becoming increasingly popular and there has been a 50% rise in the number of tattoo parlours over the same period, the NVWA said.

In April, the NVWA warned that over 40% of the black tattoo ink used in the Netherlands contains potentially carcinogenic substances.