Amsterdam - The mayors of the four largest Dutch cities have urged the Justice Ministry to close a loophole in the law that allows certain men to gain Dutch citizenship, despite having concluded polygamous marriages abroad, it was reported Frida.

The law in question applies to men of foreign origin who were born in the Netherlands and returned to their country of origin, where they concluded the marriages, and then returned to the Netherlands.

Amsterdam has long sought to have the loophole closed, and was now being joined by The Hague, Rotterdam and Utrecht, all cities with a population of whom approximately one third are Muslims.

Amsterdam has 173 persons registered as having more than one wife, although it is not known how many there are in fact.

In August, daily newspaper NRC Handelsblad reported the official statistics bureau, the CBS, considers multiple marriages as "administrative errors" and therefore deletes them from their statistics.

Labour Party (PvdA) member of parliament Jeroen Dijsselbloem twice this year called on the government to look into ways of preventing the registration of new polygamous unions.

In general, the Dutch authorities regard polygamous unions as disqualifying an applicant for naturalization.

The legal loophole occurs in the case of men born in the Netherlands. In this case, the mayor's office decides on naturalization applications.

Applicants must have no criminal record, must have been born on Dutch territory and must have resided in the Netherlands for a certain uninterrupted period. (dpa)