IOGT-NTO has been guilty of registering its members according to religious affiliation.
The Data Inspection Board (Datainspektionen) investigated IOGT-NTO methods following media reports that it had been filing members under the classification "Free Church". The registration of religious convictions constitutes a clear breach of personal data legislation, which stipulates that religious beliefs can not be recorded or registered.
The board has concluded after a review of the society's register that IOGT-NTO has broken the law. The society admitted the error and claimed that the classification was simply a marketing tool to assist the evaluation of individual members.
"We removed the details even before the data inspection board took its decision. It was an internal recruitment code to enable us to know when and where the member was recruited," said Johanna Bergkvist at IOGT-NTO.
"We realized that it could be regarded as inappropriate and we do not want anyone to think that we engage in the registration of opinions or affiliations. Furthermore we are not interested in whether people are members of the Free Church or not.
IOGT-NTO have been struggling to recruit members from the Free Church movement since pastor Åke Green was expelled for refusing to retract homophobic statements made in his sermons. The expulsion of Green was followed by a dramatic drop in members from the Free Church movement who sided with the controversial preacher.
The new scandal could harm the reputation of the temperance society among free churchgoers even further.
"Their credibility will hardly improve. You can believe their intentions, that it was just a question of marketing, but if you already have a poor reputation in a certain group then it is remarkable that they would act in this way," said Stefan Swärd of the Evangelical Free Church (EFK) to Christian website Dagen.
"It is incredibly clumsy to draw up a register such as this. Everyone knows that it is very sensitive to register religious and political opinions," political scientist Swärd said.