A trial in Utrecht giving council wardens the power to report instances of sexual intimidation they witness on the city’s streets to the police, has resulted in just one prosecution so far.

The number of reports has increased since policing began in July, following the implementation of a law making it a crime to harass people sexually by hissing, intimidating them, making sexual remarks or following them in public places.

In July and August 35 and 30 incidents were reported to police by members of the public compared to May and June with 9 and 14, possibly as a result of publicity around the new law, the council said.

The trial, which involves a number of specially trained wardens to assess how best to implement the new law, will run until June 2025.

During five harassment-detecting operations in different areas of the city, the wardens spotted on average one or two incidences bordering on intimidation, including men hissing, staring and making suggestive remarks or comments. According to the council, these did not warrant a police report.

Two infringements of the law by minors resulted in a warning, the council said. The one report that was followed up by police concerned the intimidation of one of the council wardens who was sexually intimidated outside working hours.

The aim is to catch the perpetrators in the act, which is what makes policing the new law “complicated”,  a council spokesman told broadcaster NOS. “They have to go through a whole checklist and then to see if an action is punishable by law.”

Warden and police unions earlier expressed doubts about the viability of the law. Police union ACP called the added task “a big challenge” for wardens and said it would not be easy for wardens to catch street sex pests in the act.