Aug. 14 (UPI) — Senate Democrats are calling for an audit of President Donald Trump’s White House ballroom project, after an appeals court last week prohibited further construction on it and reports that indicate that its costs continue to surge.

Trump has long sought a White House ballroom, and unilaterally demolished the East Wing in October and began construction on what was supposed to be a $200 million, privately funded facility, attracting lawsuits alleging he needed congressional approval for the project.

On Friday, an appeals court agreed with a previous district court’s ruling that Trump lacks legal authority to construct the ballroom without congressional authorization. Earlier this week, The Washington Post reported on records indicating the Trump administration plans to spend at least $600 million on the 90,000-square-foot building, with half to be covered by taxpayers.

The developments prompted eight senior Senate Democrats, including Senate Minority Leader Chuck Schumer, to urge acting Comptroller General Williams Brown of the U.S. Government Accountability Office to conduct an audit and assessment of the ballroom project.

“The subsequent construction of a new White House ballroom represents one of the most sweeping alterations to the White House complex in modern history,” the Democrats said in a letter addressed to Brown that was dated Wednesday but made public Thursday.

“The scale of this project, the destruction of historic architecture, the opaque and unorthodox combination of public funds with private funding sources and the absence of standard federal review processes raise serious concerns about transparency, accountability and stewardship of this national landmark.”

The ballroom is one of several projects Trump has spearheaded to remake the capital in his own image, including plans for a 250-foot triumphal arch, renovating the Lincoln Memorial Reflecting Pool efforts to put his name on the the John F. Kennedy Center for the Performing Arts, all of which have faced opposition, including lawsuits, especially from historic preservation organizations..

The ballroom is the most expensive and destructive of the moves, with the East Wing already demolished.

Trump has argued that the ballroom is necessary to hold large diplomatic events, such as state dinners, as the East Room is too small, necessitating the erection of tents on the South Lawn to create capacity. From the start, Trump was adamant it would be donor-funded, telling reporters as far back as July of last year, when its price tag was only $200 million, that “no government dollars” would be used.

The price of the building has repeatedly increased since. In May, Trump told reporters that “we are putting up $400 million to do the ballroom section … We are putting that up privately.”

“Given the scale, visibility and long-term implications of this project, an independent GAO review is essential to ensure accountability, transparency and responsible management of federal resources and historic assets,” the Democratic lawmakers said in their letter.

The Democrats gave Brown until Dec. 1 to provide them with a proposed plan for the audit.

Sens. Jeffrey Merkley, Martin Heinrich, Sheldon Whitehouse, Richard Durbin, Jack Reed, Gary Peters and Patty Murray joined Schumer in signing the letter.