The top two officials at the Department of Homeland Security are serving unlawfully in their roles, the Government Accountability Office said Friday, dealing a rebuke to President Trump’s affinity for filling senior executive roles in his administration with “acting” leaders who lack Senate confirmation.

The GAO, an independent watchdog agency that reports to Congress, said Chad Wolf, the acting secretary of the Department of Homeland Security, and Ken Cuccinelli, the acting deputy, are serving in an “invalid order of succession” under the Vacancies Reform Act.

Democrats in Congress called on the two men to resign, but DHS officials rejected the findings as “baseless.”

Trump has repeatedly circumvented the Senate confirmation process by installing appointees to interim positions, and then has left them in those roles indefinitely without a formal nomination or the backing of Congress.

Cuccinelli’s formal job title — senior official performing the duties of the deputy secretary — is among the most strained in the administration. The DHS leadership chart also shows him occupying the acting director role at U.S. Citizenship and Immigration Services, a job he has had for more than a year without a nomination.

According to the GAO, Trump’s installation of Wolf and Cuccinelli violated the law because of the sequence of events following the resignation of DHS Secretary Kirstjen Nielsen in April 2019. The official who assumed the title of acting secretary at that time, Kevin McAleenan, had not been designated in the order of succession, the GAO said.

Subsequent personnel moves were also therefore illegitimate, and Wolf and Cuccinelli are serving under “an invalid order of succession,” the agency found. The GAO said that it was referring the matter to the DHS inspector general for review and that any further actions would be up to Congress and the IG’s office.

The Vacancies Reform Act governs how temporary appointments can be made to positions that require Senate confirmation.

Immigrant advocacy groups already have challenged the legality of Trump administration initiatives by arguing the policies have been implemented by DHS officials who lack legal authority to do so. The GAO finding is expected to trigger a new wave of litigation calling into question DHS policy changes that include blocking asylum seekers, immigrants and others from entering the country.

DHS quickly issued a statement challenging the GAO’s conclusion Friday.

“We wholeheartedly disagree with the GAO’s baseless report and plan to issue a formal response to this shortly,” DHS spokesman Nathaniel Madden said.

The normal nomination process exists in part to encourage executive nominees who will be acceptable to a majority of lawmakers while preserving the congressional oversight role the Constitution established. Trump has said he prefers having senior officials serving in an acting capacity because he thinks it makes them easier to remove.

“I like ‘acting,’ ” Trump told reporters last year. “It gives you great, great flexibility.”

The president’s unprecedented disdain for the norms of the confirmation process is especially notable because his own party enjoys a majority in the Senate.

Despite the GOP’s control of the Senate, some of the top officials Trump has appointed, including Cuccinelli, would not be able to win majority support there. Senate Majority Leader Mitch McConnell (R-Ky.) warned the White House last year that he would not allow Cuccinelli to be confirmed because of Cuccinelli’s prior campaign work targeting moderate Republicans.

The GAO report newly emboldened Democratic lawmakers in going after Trump’s appointees and the work they have done while in the Trump administration.

“The determination by an independent congressional watchdog today invalidates actions Mr. Cuccinelli and Mr. Wolf have taken and both should immediately step down from their illegal roles,” Senate Minority Leader Charles E. Schumer (D-N.Y.) said in a statement. “The Department of Homeland Security Inspector General must launch a top-to-bottom legal review of every decision made by Mr. Cuccinelli and Mr. Wolf during their tenures and report his findings to the public and to Congress.”

Wolf was a deputy chief of staff at DHS before rising through the ranks of the department. He was not Trump’s first choice for the job, but neither Cuccinelli nor acting Customs and Border Protection commissioner Mark Morgan were eligible for the acting secretary role.

Instead, Wolf was narrowly confirmed for the top policy job at DHS in November and installed in the acting secretary role the same day. He has played a central role in the government’s controversial response to protests throughout the United States this summer, actions some former DHS officials from both parties have said crossed the line.

Cuccinelli, formerly the attorney general of Virginia, has impressed the president with his forceful advocacy for Trump’s immigration policies during television interviews. In March, a federal judge ruled that his appointment to lead USCIS was illegal and that he lacked the authority to issue policy directives tightening asylum rules. The Trump administration dropped its appeal of that ruling Thursday.

The GAO noted that it was not examining the question of the consequences of Wolf and Cuccinelli’s improper appointments, nor the impact of their installation on the actions they have taken in those roles, instead referring those questions to the DHS inspector general.

The GAO conducted its review in response to inquiries from House Homeland Security Committee Chairman Bennie Thompson (D-Miss.) and House Oversight and Reform Committee Chairwoman Carolyn B. Maloney (D-N.Y.).

In a statement responding to the GAO’s findings, Thompson and Maloney called on Wolf and Cuccinelli to resign from their roles.

“GAO’s damning opinion paints a disturbing picture of the Trump administration playing fast and loose by bypassing the Senate confirmation process to install ideologues,” Thompson and Maloney said. “In its haste to circumvent Congress’s constitutional role in confirming the government’s top officials to deliver on the president’s radical agenda, the administration violated the department’s order of succession, as required by law.”

Since Trump ousted Nielsen in April 2019, the White House has displayed an unprecedented disregard for the Senate confirmation process. McAleenan served seven months without a nomination, and though Trump has effusively praised Wolf, he has not received a nomination for the secretary position.

Across the department, career officials have retired or resigned from their jobs without replacement, and the White House has made no effort to push for the confirmation of its more-recent appointees.

The leadership page of the DHS website shows empty seats and interim appointments across the agencies charged with protecting the country from terrorist attacks and other threats, with more than 20 vacancies and acting chiefs among senior department positions.

In addition to the temporary appointments at DHS headquarters, none of the three agencies that run the country’s immigration system — U.S. Customs and Border Protection (CBP), U.S. Immigration and Customs Enforcement (ICE) and U.S. Citizenship and Immigration Services (USCIS) — have a Senate-confirmed leader.