The Oslo diocese and two officials, the bishop and the financial officer, are suspected of fraudulently registering thousands of people on its membership lists between 2010 and 2014, which enabled it to obtain 50 million kroner (more than $6.0 million or 5.8 million euros) in state subsidies.
In Norway, a predominantly Protestant country, the state provides subsidies to organised religions, the size of which is determined by the number of members.
"The opinion of the diocese is that we have done nothing illegal," the interim head of the Church, Lisa Wade, said at the presentation of the Church's report on the affair.
Police have accused the Oslo diocese of going through the telephone directory in search of immigrants whose names appear to signal that they come from Catholic countries, and adding them to the membership list, sometimes without their knowledge.
Norway's Roman Catholic minority had 140,000 registered members in 2014, more than double the number in 2010.
To explain the jump, the Church has claimed it benefitted from a large wave of Catholic immigrants, notably Poles, who practised their religion but did not register with the Church, which in turn cost the Church more but did not result in increased state subsidies.
"The diocese never intended to do anything other than identify the Catholics in the country," Wade said. "Unfortunately, the method that was used led to some incorrect registrations," she added.
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Wade said 7,000 people had been mistakenly registered, including Catholics who did not want to be included on the list and non-Catholics. Their names have now been removed from the list.
More than 21,000 other cases have yet to be clarified. Police raided the Catholic Church's offices on February 26 on suspicions of "aggravated fraud.”