Senators have approved new legislation which will impose a one-off fee on class four insurance companies.

The Insurance Companies (Special Fees) Act 2010 brings in the charge to cover the costs of enhanced supervisory standards.

Attorney General Kim Wilson told the Senate on Monday: "The insurers affected have been broadly consulted with respect to these fees and understand the importance of this revenue-generating effort."

She said 37 companies would have to pay between $80,000 and $280,000, depending on their gross payments received.