Amsterdam’s borough council of Zuid is to ask people who use the area’s massage salons about their experiences, in an effort to find out if they are a front for illegal prostitution.

Council wardens are also to keep a better eye on salons which are suspected of offering ‘happy endings’, the Parool says on Monday. It is the first time city officials will have taken an ‘undercover’ approach to dealing with massage salons, the paper says.

Over the past year, nine addresses in Zuid were checked by council inspectors and nine were closed down for periods of three months. One case, which centres on an internet review by a satisfied customer, is still pending in court.

The closures are the result of a major effort to clamp down on massage parlours which also offer prostitutes and form unfair competition for licenced brothels. In total, checks were carried out on 22 massage salons – mainly operated by Thai and Chinese nationals.

Officials checked for ‘signs’ of prostitution as well as ‘scantily clad women’ and ‘sex-related objects’, the Parool said in January.