A bipartisan group of attorneys general on Wednesday said they oppose the National Park Service's proposal to more than double visitor fees for 17 popular national parks.

The attorneys general include Xavier Becerra of California, a Democrat, Mark Brnovich of Arizona, a Republican, Democrat Eric Schneiderman of New York, and eight others.

“The service’s proposed fee increases, which double or even triple existing entrance fees, threaten to put many Americans to the choice of beauty or bread and to distance them from the places in which so many experience the natural wonder of our great and unique nation,” they wrote in comments filed Wednesday in which they quoted famed conservationist John Muir. “This is concerning as a matter of policy.

“As a legal matter, the service has not offered a reasoned explanation for its proposed fee increases and its actions are inconsistent with the laws that govern our national park system,” the attorneys general said. The other states signing the comments are Maine, Maryland, Massachusetts, New Mexico, Oregon, Rhode Island, Washington, and the District of Columbia.

Under the proposal, the entrance fee for the Grand Canyon and other parks would rise from $30 to $70 per vehicle. Other parks would even bigger increases, from $25 to $70, during the busiest months of the year. Zion and Arches in Utah, for example, would impose those fees from May through September, while Maine's Acadia and Virginia's Shenandoah national parks would charge the higher prices in June through October.

The increases are meant to fund the $12 billion maintenance backlog at national parks and other infrastructure upgrades, the Interior Department says.

Democrats and national park groups have criticized the proposal, arguing Congress or the administration should pay for the maintenance at national parks, not visitors.

A Senate appropriations bill for next year released Monday would increase the National Park Service budget to include funding for the construction backlog at national parks.

The agency originally planned to accept comments through Thanksgiving, but its new deadline is Dec. 22.