WASHINGTON – Secretary of State Mike Pompeo made a secretive trip in January to a Florida retirement enclave populated by prominent GOP donors at the tail end of a diplomatic trip to Latin America.

He held the same kind of quiet meeting in December with Republican donors at a hotel dinner on a State Department trip to London.

And last October, he huddled with Charles Koch, the GOP billionaire and a longtime supporter of his, while on an official visit to Kansas. That trip was made aboard a government aircraft.

In each of those instances, Pompeo did not put the visits on his public schedule. He and his aides avoided telling the reporters with them about the meetings, though some reported them afterward. And they took place as Pompeo was considering a run for the Senate from Kansas and as he nurtures plans for a presidential bid in 2024.

Pompeo, President Donald Trump’s most loyal and powerful aide, has not tried to hide his political ambitions. But he has chosen not to disclose certain meetings that appeared to be linked to those plans while on taxpayer-funded trips. The exact number of the meetings is unclear.

For some of Pompeo’s official travels, the State Department does announce that he meets with U.S. corporate leaders — that was the case when the secretary visited finance sector executives in New York City in early March — but the department gives no further details.

Such activities are coming under greater scrutiny after congressional aides said that the State Department inspector general, Steve Linick, who was fired by Trump last Friday at Pompeo’s urging, had opened an investigation into potential misuse of department resources by Pompeo for personal benefit.

Some GOP allies defend Pompeo’s meetings with political and corporate figures on official trips. “What’s he supposed to do — not reach out and have social interaction with business leaders because his name has been associated with the presidential race? It’s part of the job,” said Alan Cobb, president and chief executive of the Kansas Chamber of Commerce and a longtime friend to Pompeo and his wife, Susan. “And the fact is, most wealthy business leaders are political donors — good luck finding one who is not.”

Yet Pompeo’s political meetings — and his domestic travels under State Department auspices — have attracted the attention of critics who accuse him of pursuing a personal agenda on taxpayer money.

American Oversight, a liberal legal watchdog, has demanded that the State Department turn over details of all of Pompeo’s domestic trips.

“It’s becoming increasingly clear that Secretary Pompeo is using the State Department to support his political career, and is using the position of secretary to collect a Rolodex of powerful people to support him for whatever venture he sees next,” said Austin Evers, the group’s executive director, who worked at State during the Obama administration.

Congressional aides said they had noted Pompeo’s unannounced side visits while on diplomatic business. Sen. Bob Menendez, D-N.J., called for a special counsel investigation last year into the legality of Pompeo’s frequent Kansas trips. The Hatch Act forbids federal employees from using their official positions to carry out partisan political activities, with the exception of the president and vice president.

Pompeo has not accepted any donations to his political campaign committee, and he has refunded about $3,000 in contributions since he joined the Trump administration, according to Federal Election Commission records.

It is unclear which of the investigations of Pompeo and his aides by the Inspector General’s Office, if any, prompted Pompeo to recommend the firing of Linick, who had served as inspector general since 2013, and whether the move was an act of retaliation to shield himself from accountability. Pompeo has said it is “patently false” that his actions were in retaliation against Linick because of any inquiries.

Democratic leaders in Congress have opened an investigation into the firing — they have demanded that agencies turn over relevant documents — and some Republicans have criticized Trump’s move.

The president appointed an ally of Vice President Mike Pence, Stephen Akard, to be the acting inspector general. Akard went to the office on Monday, despite the mandatory 30-day congressional review period over Trump’s actions, and told people there that he would keep his ambassador-level State Department job, as head of the foreign missions office, while serving as inspector general.

In his new post, he would oversee a staff of hundreds working on inquiries into fraud and waste at the agency. Congressional aides said holding both positions is a conflict of interest.