AUGUSTA – Twenty state employees have filed a federal lawsuit challenging fees nonunion members of a 10,000-member state workers’ union must pay in lieu of dues.

The National Right to Work Legal Defense Foundation is providing legal assistance for the workers, whose lawsuit seeks to block compulsory payments of union dues by workers who are not union members, but receive union protection.

The lawsuit, filed Wednesday in U.S. District Court in Portland, names the Maine State Employees Association and some senior state officials as defendants. It asks the court to block fee collections until the union provides an independent audit of its expenditures.

It also asks that MSEA pay back all of the past payments, which are equal to weekly dues paid by union members, not including what’s spent for political purposes.

MSEA President Dana Graham said the “fair share fees” have been upheld in the courts and are “perfectly legal.” Graham also said the union has made available all of the financial information it’s obligated to disclose.

He deferred further comment until union officials have seen the lawsuit, which seeks class-action status.