The tax office can keep the source of a list of illicit bank accounts held by Dutch nationals in Luxemburg confidential, the Dutch Supreme Court said on Friday.

In addition, the anonymity of the source is not sufficient reason to tear up the fines handed out in connection with the case, the court said.

The list led to 61 people with money in various bank accounts in Luxemburg being fined for hiding their savings from the Dutch tax authorities.

The civil servants were earlier ordered to come clean by the lower courts but refused to state the source of the information on finance ministry instructions.

The case dates back to 2009 when then junior finance minister Jan Kees de Jager bought a list of people with secret foreign bank accounts from the anonymous source. The finance ministry has collected an estimated €1.6bn in back taxes and fines from people with secret bank accounts abroad.

Current junior tax minister Eric Wiebes welcomed the ruling. ‘If the tax office has to release the names of tipsters, there won’t be any more tipsters and therefore no tips,’ he said.