The foreign ministry has been accused of obstructing a criminal inquiry into corrupt payments by a Dutch building firm to the Saudi royal family.

The Telegraaf newspaper reported in 2013 that Ballast Nedam had paid hundreds of millions of euros to a member of the House of Saud to secure military building contracts on the Arabian peninsula. The bulk of the money, some $450 million, went to Prince Alwaleed bin Talal Alsaud.

Documents obtained recently by the TV station Human revealed that the ministry of foreign affairs blocked an attempt by the Dutch tax service’s fraud division (FIOD) to interview a Saudi witness during its investigation of the case.

According to the document, which is the basis of a documentary broadcast on Monday, the interview was abandoned ‘because of bilateral relations, the status of those concerned and the possible risks to the witness who was to be heard.’

Investigators in the case told the Telegraaf that they had been frustrated by the ministry’s intervention. The then foreign affairs minister Frans Timmermans denied any interference in the case when the issue was raised by Socialist MP Harry van Bommel.

‘The Netherlands’ interests in Saudi Arabia, whether diplomatic, economic or of any other kind, have not been allowed to have any kind of influence on the criminal investigation into the illegal payments affair,’ said Timmermans when questioned by the Telegraaf.

Ballast built two airfields in Saudi Arabia for a total sum of $580 million. FIOD believes the contracts were only worth $249 million and the illegal payments made up the difference.