Pence's stay at Trump property in Ireland is focus of Senate Democrat inquiries One senator told Pence he was "troubled by the apparent conflict of interest."

Vice President Mike Pence's stay at a property in Ireland owned by the president's company has prompted a Senate Democrat to question if the taxpayer-funded visit was cost effective and to label it an "apparent conflict of interest."

Sen. Gary Peters, D-Mich., the ranking member of the Senate's Homeland Security and Governmental Affairs Committee, sent a letter to the vice president on Thursday asking for specific information on the costs of Pence's stay at Trump International Golf Club in Doonbeg, including comparable rates for hotels nearby and across the country in Dublin, where Pence held meetings with Irish officials and business leaders.

On Wednesday, Democratic presidential candidate Sen. Elizabeth Warren sent a letter to Secretary of State Mike Pompeo requesting more information about the trip, which she called "another example of what appears to be open corruption" in the Trump administration.

Peters told Pence in his letter, first obtained by ABC News, that he was "troubled by the apparent conflict of interest in your decision to stay at a property owned by President Trump, which creates the risk that taxpayer funds are being used to directly profit the President."

Pence on Tuesday defended visiting his family's Irish hometown and staying at President Donald Trump's property there at taxpayer expense, arguing the resort was a "logical" choice that let him highlight Irish-American ties.

The vice president held official meetings with Irish leaders in the nation's capital, but flew back and forth across the country in Air Force Two to spend nights in the small village of Doonbeg, where his cousin runs a bar and his great-grandmother grew up.

"I find it hard to believe that your office was unable to identify lodgings that could accommodate the security and logistical needs of your trip in the capital of Ireland," Peters wrote.

The vice president was accompanied by his mother, wife and sister on the official trip. Pence's chief of staff, Marc Short, said Tuesday that the vice president was "personally paying" for his sister and mother's expenses, according to a reporter traveling with the vice president.

Peters also requested information on Pence's relatives' expenditures and his reimbursements.

"Unfortunately, your travel to President Trump's golf club is part of a troubling trends," Peters wrote. "Reports now claim that at least 24 of the 32 individuals who have served in the President's Cabinet have patronized Trump properties, including the Trump International Hotel in Washington, DC -- another property owned by the President."

Warren wrote in her letter to Pompeo -- released by her office Thursday -- that Pence's stay amounted to a "transaction."

She asked Pompeo to provide information about Pence's Doonbeg visit and the State Department's approval of the plans.

House Democrats also plan to look into the matter as part of their probe into violations of the Emoluments Clause. The clause prohibits American office-holders, including the president, from personally profiting from foreign governments and has been a topic of discussion since Trump took office.

The House Judiciary Committee announced last week they will investigate any administration plans to host next year's G-7 summit at Trump's Miami resort and golf club. In a statement, Chairman Jerry Nadler and Rep. Steve Cohen said the panel would schedule new hearings and request information from the White House as part of the probe.

Attorney General William Barr is hosting a holiday party at the Trump Hotel in December. However, a Justice Department official told ABC News that he is paying for the $30,000 holiday party himself and added that the purpose of the party is not to curry favor with the president.

Asked on Tuesday if the president asked Pence to stay at his property, the vice president's chief of staff, Marc Short, told reporters that he did not think it was "a request, like a command" -- but rather "a suggestion."

"It's like when we went through the trip, it's like, well, he's going to Doonbeg because that's where the Pence family is from," Short said Tuesday. "It's like, 'Well, you should stay at my place.'"

Early Wednesday, though, the vice president's office followed up with a statement from a spokesperson who said "the decision to stay at" the resort "was solely a decision by the Office of the Vice President and was based on the requirement to find accommodations near the Vice President’s ancestral hometown that could satisfy official meetings on both coasts of the Emerald Isle."

Trump on Wednesday said he had "no involvement" in Pence's decision to stay at his resort.

"From what I understood, he was going there," Trump said. "Then I heard he was going there, but I didn't -- it wasn't my idea for Mike to go there. Mike went there because his family is there. That's my -- that's my understanding of it."

Asked if he suggested Pence stay there, Trump replied, "No, I didn't -- I don't suggest anything. I don't suggest it."

The president on Wednesday also denied ever speaking to Barr about using his hotel in Washington.

"With Mike Pence, we never spoke about it and with Bill, I never spoke about -- Attorney General Barr, we never spoke about it," Trump said. "But, that's what they choose."