The four parties in talks on forming a new Dutch government do not want the planned rise in the health insurance own-risk element to go up to €400.

Chief negotiator Gerrit Zalm has written to health minister Edith Schippers to say the four parties oppose the increase. He has taken the unusual step because any change has to be made formal in law by October 1.

The size of the own-risk payment – currently €385 – is important for health insurance companies when they determine what premiums to charge patients next year. Patients have to first spend €385 on healthcare themselves before they can claim on their health insurance for treatment.

Caretaker health minister Edith Schippers says the decision not to increase the own risk means that all adults will have to pay an extra €10 a year in premiums. She had earlier indicated that premiums would go up by an average of €6 a month.

The government determines what is covered in the basic healthcare insurance package but insurers are free to set their own fees.