"This admission fee sets a harmful precedent for future permanent exhibits, making it difficult to deny the other Smithsonian entities that right and may encourage other Smithsonian entities to structure their exhibits to fit the Butterfly Pavilion model," Norton said Monday.

"Admission fees are not the answer for taxpayers, who have already paid through the federal government's 70 percent contribution to this public institution's annual budget," she added. "Federal taxpayers do not expect to pay again through an admission fee to a federally financed institution."

Norton's bill would require the Smithsonian to submit a report to Congress about any proposed fees it is considering, and to submit a plan to Congress for funding the butterfly exhibit without the use of fees.

Norton also proposed the Smithsonian Modernization Act, H.R. 2620, which would expand the Smithsonian's Board of Regents and ensure it is made up of only private citizens. Today, more than half of the board is made up of public officials, including six members of Congress, the vice president of the United States and the chief justice of the Supreme Court.

Norton said private citizens on the board should have more experience with private fundraising, to help the Smithsonian fund exhibits without having to charge fees.

A third bill from Norton, the Open and Transparent Smithsonian Act, would ensure accountability of the public money the institution receives. H.R. 2622 would do that by subjecting the Smithsonian Institution to the Freedom of Information Act and the Privacy Act.