Health ministry civil servants in 2012 decided not to give parliament details about secret deals with pharmaceutical companies about the cost of expensive drugs, the Telegraaf says on Thursday.

The decision was taken before officials started negotiations with two drugs firms about drugs for tens of thousands of people with thrombosis, the paper says. It bases its claim on internal documents.

Despite internal rules calling for maximum transparency, health minister Edith Schippers went ahead with the secrecy, the Telegraaf says. In addition, drugs company Böhringer Ingelheim was allowed to contribute to the official letter to parliament outlining the deal.

Schippers eventually told parliament the agreement, in which her ministry agreed to buy the drugs directly for a very large discount, had led to savings of ‘several tens of millions of euros’.

Socialist MPs have called on the ministry to explain.