U.S. Sen. Jon Tester on Wednesday criticized a proposal by the National Park Service to increase entrance fees at both Glacier and Yellowstone national parks, saying it was the duty of Congress to fund repairs.

The National Park Service, under the leadership of Interior Secretary Ryan Zinke, said this week it was considering fee increases at 17 of its most popular parks, most of them located in the West, to address a growing backlog of maintenance and infrastructure needs.

But opponents, including Tester, said the increases are too high and could lock out thousands of visitors who are unable to cover the steep entry fees.

“Americans already own these parks and they shouldn’t have to empty their wallets to enjoy them,” Tester said. “This decision will price Montana families out of our public lands and hurt local economies, which thrive thanks to our national parks.”

Summer entrance fees for both Yellowstone and Glacier stand at $30 per vehicle and $25 per motorcycle. The Park Service’s proposal would double those rates to $70 per vehicle and $50 per motorcycle during the “peak season,” which includes the five months when visitation is at its highest.

The latest proposal comes after many national parks that charge entrance fees raised them. Then, like now, the need was the same – to address the parks' growing list of maintenance and infrastructure projects.

The Park Service has estimated that deferred maintenance across its parks stands north of $11 billion.

“We need to have a vision to look at the future of our parks and take action in order to ensure that our grandkids’ grandkids will have the same if not better experience than we have today,” Zinke said in a statement. “Shoring up our parks’ aging infrastructure will do that.”

Tester said Congress has a responsibility to fund the longstanding maintenance backlog of National Park Service sites without imposing drastic fee increases on visitors.

A 30-day public comment period will remain open through Nov. 23. Those wishing to offer public comment can do so on Tester's congressional website.

“Glacier and Yellowstone should be accessible to all of us,” Tester said. “I encourage all Montanans to weigh in and make their voices heard.”