The U.S. Department of Agriculture (USDA) may have violated the law with its decision to relocate two offices from Washington, D.C., to the Kansas City area, according to the USDA Office of Inspector General (OIG).

The USDA recently moved its National Institute of Food and Agriculture and Economic Research Service offices, saying the change was financially sound and put its researchers closer geographically to American farmland.

However, the move was met with widespread pushback from employees of the affected offices, who unionized in response to the announced move, with many publicly turning their backs on Agriculture Secretary Sonny Perdue.

The USDA has instructed all affected employees to report by Sept. 30 and has rejected a union proposal to let some employees to continue working from Washington.

The USDA's general counsel, Stephen Vaden, has argued that the department is not bound by laws requiring it to secure congressional approval to spend the money to relocate, claiming the law in question is unconstitutional.

The inspector general's report counters that Vaden's claim is "not consistent with prior positions taken by the Department."

"To reach management decision on this recommendation and to ensure consistent treatment going forward, the Department needs to communicate, in writing, this change of interpretation to USDA leaders at the Sub-Cabinet and Agency levels," the report states.

In a comment to The Hill, the USDA said, "The Department is not required to abide by provisions that have been deemed unconstitutional, therefore we will not take the OIG's recommendation to ignore nearly forty years of precedent set by the Supreme Court, Office of Legal Counsel, and the Government Accountability Office - an arm of Congress."

"Since the Inspector General affirms the Department has the legal authority and we do not agree with the unconstitutional budgetary provision, this case is closed. This is opinion based on policy decisions that have no basis in fact," the department added.

Senate Democrats previously questioned a USDA official over the planned move, with Sen. Debbie Stabenow (D-Mich.) suggesting it was a stealth purge of research staff.

"It's clear to me that this is not a relocation. It's a demolition. It's a thinly veiled, ideological attempt to drive away key USDA employees and bypass the intent of Congress," Stabenow said at a July hearing of the Senate Agriculture, Nutrition and Forestry Committee.