pabradyphoto/iStock(WASHINGTON) -- An independent government watchdog says the Interior Department violated spending laws by using money meant for maintenance and improvements in national parks to pay for day-to-day operations during the government shutdown.

During the shutdown in December and January, the Interior Department decided to tap into a fund of money collected from fees in National Parks to pay to keep the parks open and help collect trash and protect them from damage. Democrats in Congress opposed the decision saying the administration was using money meant to help the maintenance backlog in national parks.

The Government Accountability Office found the department violated laws on the use of appropriated funds by using that fee money for operations that normally would have been part of its congressionally appropriated budget, specifically trash collection and restroom maintenance. Violations of the Anti-Deficiency Act are technically a criminal violation but are not frequently prosecuted.

"Interior disregarded not only the laws themselves but also the congressional prerogatives that underlie them. Instead of carrying out the law, Interior improperly imposed its own will," the GAO said in its official finding.

The finding also said any future use of FLREA funds using the same argument will be considered a "knowing and willful" violation of the law and could result in penalties for officials involved.

The finding released on Thursday only applied to the government shutdown, but the Interior Department also authorized $2.5 million from the same fund to be used for the "Salute to America" event on the Fourth of July.

Democrats Rep. Betty McCollum and Sen. Tom Udall, who sit on the respective appropriations committees that control Interior's budget, originally asked for the GAO opinion.

"The Administration should now immediately report this violation and take corrective actions as required by law. This should put the administration on notice that their illegal actions will not be tolerated. As stated in the GAO opinion: 'With this decision, we will consider such violations in the future to be knowing and willful violations….' and I agree," McCollum said.

According to the GAO finding the department will have to officially report the violation, identify the officials responsible and adjust its accounts to correct the violation.

In a statement sent to ABC News, Interior spokeswoman Melissa Brown said, "It's obvious that the GAO reached their conclusion prematurely and without regard for all of the facts. We completely disagree with the GAO's erroneous opinion regarding our appropriate and lawful use of FLREA funds. The Department acted well within its legal authority to clean up restrooms and pick up trash, so the American people could enjoy their National Parks."

The GAO said officials contacted Interior to provide its legal views on the matter and response, but the department did not respond.

"The Department was in ongoing conversations with GAO regarding our response, which they knew was in process," Brown said. "The report's characterization of our lack of cooperation is blatantly false."

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