A Dutch court on Wednesday outlawed an association which lobbies for the social acceptance of sexual relations between adults and children.

"The court has banned and ordered the dissolution" of the Martijn organisation, a spokesperson for the civil court in the northern city of Assen, Luta van der Leij, told AFP.

The court said in a statement Martijn glorified sex with children as "something normal and acceptable, or as something that should be."

"The court finds lobbying for these rights is a grave infraction of the values of our society," it said.

Dutch prosecutors on 16 May in closing arguments called for the organisation — which has been around since 1982, to be banned and dissolved.

With its headquarters in Assen, about 160 kilometres northeast of Amsterdam, and running a website, prosecutors said Martijn "offered a digital network and office to sex offenders".

Currently it has about 60 members and lobbies for what it termed consentual sex between adults and children, while stating it is vehemently opposed to sexual abuse.

Its former president Ad van den Berg was jailed for three years on 18 October last year in Harlem in western Netherlands for possessing pictures, films and magazines featuring child pornography.

The prosecution took the civil case to the Assen court after an appeals court in November last year refused to prosecute Martijn on criminal charges.

Martijn's current president Marthijn Uittenbogaard told AFP the court's decision was a "black day for the freedom of expression and the rule of law," adding "we will talk to our lawyers now to see what to do next".

Its defence lawyer Bert Swier said on 16 May it would appeal should the decision go against Martijn.

The Assen civil court, however, said: "Martijn violates children's rights, where the protection of childrens' sexual rights unmistakably forms one of the most desirable principles of our legal system."

It said children were "unable to adequately resist adults making sexual advances" and that is why there were "morality laws to protect them".

The prosecution's office said in a statement it was satisfied with the ruling, adding it had made the point that "the workings and ideas of Martijn were contrary to the public order and good morals".