WASHINGTON (WASHINGTON POST) - Last month, US Attorney-General William Barr booked President Donald Trump's Washington DC hotel for a 200-person holiday party in December that is likely to deliver Trump's business more than US$30,000 (S$40,000) in revenue.

Barr signed a contract, a copy of which was obtained by The Washington Post, for a "Family Holiday Party" in the hotel's Presidential Ballroom on Dec 8.

The party will feature a buffet and four-hour open bar for about 200 people.

Barr is paying for the event himself and chose the venue only after other hotels, including the Willard and the Mayflower were booked, according to a Department of Justice official.

The official said the purpose of Barr's party was not to curry favour with the president.

Barr holds the bash annually and it combines holiday festivities and a "ceilidh", a party featuring Irish or Scottish music.

"Career ethics officials were consulted and they determined that ethics rules did not prohibit him from hosting his annual party at the Trump hotel," said the official, who spoke on the condition of anonymity because the party is not a Justice Department event.

Barr's decision to book his boss' hotel marks the latest collision between Trump's administration and his business, which the president no longer operates but from which he still benefits financially.

Trump said on Monday that he was likely to hold next year's Group of Seven (G-7) international summit at his golf resort in Doral, Florida.

Already the federal government and GOP campaigns have spent at least US$1.6 million at his properties since he entered office, according to a Post analysis, though the actual figure is likely to be higher because of the difficulty of obtaining up-to-date records.

Barr, the nation's top law enforcement official, has previously made misleading statements regarding special counsel Robert Mueller's report that echoed those of Trump, leading experts to question Barr's independence from the president.

"It creates the appearance that high-level political appointees or allies of the president may feel like they need to spend money at the president's businesses as a show of loyalty, and that is something that makes me deeply uncomfortable and should make taxpayers deeply uncomfortable," said Liz Hempowicz, director of public policy at the non-profit Project on Government Oversight.

The Trump Organisation declined comment.

Representatives from the Willard Hotel declined to comment, citing the company's privacy policy.

A spokeswoman for the Mayflower Hotel did not immediately respond to a request for comment.

Barr's decision to book the Trump hotel is noteworthy in particular because Justice Department attorneys are defending the president's business in court.

Trump's DC hotel has hosted a number of foreign governments as clients, business that has generated two lawsuits, one from the attorneys-general of Maryland and DC and the other from about 200 Democratic members of Congress.

Both cases are being considered in federal court, and the Justice Department is defending the president's position that he has not run afoul of the anti-corruption provisions in the Constitution called the domestic and foreign emoluments clauses.

DC Attorney-General Karl Racine, a Democrat, a plaintiff in one of the emoluments cases against Trump, said Barr's plans make him fear "that all this does is it normalises conduct of presidential supporters or would-be supporters, who clearly know a clear avenue to curry favour with the president and that is to do business with the president's business."

White House aides, including inside the White House Counsel's office, have warned Trump and Cabinet officials against making official visits to his properties.

NOT AN OFFICIAL EVENT

Barr's event falls into a different category. It isn't an official event - it's a party. His contract requires that he spend US$4,500 to rent the ballroom - space designed by Ivanka Trump before she joined her father in the White House - and US$135 per person for a buffet and open bar, a number that is likely to adjust after Barr chooses a menu for the event.

Walter Shaub, a former director of the Office of Government Ethics who has been an outspoken critic of Trump's ethics record, called Barr's decision to book Trump's hotel "one of those things that doesn't violate the rules but it's really troubling."

"He keeps sending signals that his loyalty is to a politician and not to the country," Shaub said.

"And it's part of an ongoing erosion of credibility at the Department of Justice."

It is difficult to determine whether Barr will pay market rate for the event, as the Justice Department official asserted he would. The contract, sent to Barr at his northern Virginia home, calls for a minimum of US$100 per person for food and beverage before adding 35 per cent for taxes and tip. It requires that Barr pay at least pay US$31,500 even if he cancels the event.

The hotel's publicly available menu lists a "banquet dinner" as costing US$115 per person for two hours plus US$30 for each additional hour. A hosted bar costs US$29 for the first hour per person and an additional US$12 per hour for each additional hour. If Barr opts for that level of service at those prices, the food and beverage bill for 200 guests would likely top US$45,000.

Hotels typically have lots of available space on Sunday nights, leading them to offer less expensive rates. A contract the hotel signed with Virginia Women for Trump for a Monday event in the summer of 2018, obtained separately by the Post, required a US$3,050 room rental fee and US$39,000 banquet fee for a much larger group, 818 people, though it did not include an open bar.

Hempowicz said that if Barr receives a discount from the hotel it would give other Americans dealing with the Justice Department reason for concern, whomever the party is for.

"If the attorney-general gets a discount while the Justice Department defends the hotel in court, that is not how the justice system is supposed to work and its not how the Department of Justice is supposed to work," she said.