The House Oversight Committee is investigating an allegation that at least one foreign government and one trade association booked rooms in US President Donald Trump's hotels and left them empty, Politico reported.

The committee is probing whether this violates the US Constitution's Emoluments Clause, which prohibits the president from receiving gifts or cash outside their salary, Politico said.

The probe forms part of the House's impeachment inquiry into the president.

Many US officials, including Vice President Mike Pence and Attorney General William Barr, have shown preferences to stay at or do business with Trump properties in the past.

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Officials from at least one foreign government and one trade association may have booked rooms in US President Donald Trump's hotels without staying in them in order to curry favor with him, Politico reported.

The allegation is part of the House Oversight Committee's investigation into whether by taking money from US or foreign government officials at his businesses, Trump broke the law, according to the news site.

The US Constitution's Emoluments Clause prohibits public officials from receiving gifts or cash from foreign or US officials without congressional approval.

Trump International Hotel in downtown Washington. Pablo Martinez Monsivais/AP

The committee's probe came after it received a tip that the trade association and foreign government, which are separate entities, had booked a large amount of rooms but only used a small number of them, Politico reported, citing an unidentified person familiar with the allegation.

The report did not name the Trump hotels that were allegedly booked.

The House Oversight Committee has not yet responded to Business Insider's request for details on the allegation and the name of the hotels involved.

The White House and Trump Organization have not yet responded to Business Insider's request for confirmation and comment on the allegations and House investigation.

Trump in the Oval Office on September 30, 2019. Jabin Botsford/The Washington Post via Getty Images

The investigation forms part of the House's larger official impeachment inquiry into the president, Politico reported. The probe, opened by Speaker Nancy Pelosi last week came in light of a revelations that Trump repeatedly pressed Ukraine's president to investigate his 2020 rival Joe Biden and his son over corruption allegations.

Read more: Business Insider's full coverage of the Trump's Ukraine call and the whistleblower scandal

It is unclear whether Trump or his staff had actively asked for or encouraged the hotel reservations, or whether the trade association and foreign officials made the bookings of their own volition.

If Trump or his staff asked for the two entities to make the reservations, then they could have broken the law.

But even if they hadn't, it would reflect a "culture of corruption that the administration has created," said Rep. Ro Khanna, a Democratic member of the House Oversight Committee, according to Politico.

"There's a sense that to curry favor you have to engage in pay to play," he said. "That's exactly what the American people hate about Washington."

Rep. Gerry Connolly, another Democratic member of the committee, also described the bookings as "an obvious attempt to curry favor" with Trump, Politico reported.

"Now we're looking at near raw bribery," he added.

An aerial view of the Trump luxury golf resort in Doonbeg, Ireland. Courtesy of Trump International Golf Links & Hotel

Read more: Inside Trump's controversial luxury golf resort in Ireland, where Pence spent US tax dollars and sparked outrage

Trump has been the subject of multiple investigations into whether he had violated the emoluments cause. He still owns all his businesses, but placed his holdings in a blind trust designed to hold his assets shortly before becoming president.

Here are some recent examples of US officials showing preferences to Trump properties:

An Air National Guard crew stopped at Trump Turnberry, the president's luxury golf resort in Scotland, to refuel during a supply trip from the US to Kuwait, Politico reported last month. The House Oversight Committee is investigating this trip.

During an official trip to Ireland last month Vice President Mike Pence and his staff stayed at the Trump International Golf Links and Hotel in Doonbeg, despite its location on the opposite side of the country from Dublin, where Pence's meetings were held. Trump had suggested that Pence stay at the resort, Reuters reported at the time, citing a Pence representative.

Attorney General William Barr reportedly booked Trump's Washington, DC, hotel for a holiday party that would cost more than $30,000, The Washington Post reported.

The president and his family members also visit Trump Organization properties frequently.