Donald Trump Jr.'s ex-fiancée has used her ambassadorship to promote one foreign firm while keeping its paid lobbyist at her side.

Kimberly Guilfoyle, whom President Donald Trump named ambassador to Greece, has repeatedly pressed Balkan governments to work with Aktor Group, The Wall Street Journal reported on Friday. Aktor is a Greek construction company that only recently moved into the natural gas business.

Christos Marafatsos, who lobbies for the firm, has joined Guilfoyle at so many meetings that some foreign officials took him for her chief of staff.

Federal lobbying records show Aktor paid Marafatsos $160,000 through June to build ties with the White House and the State and Energy departments. Several people who met with the pair, including government officials, told The Journal he never disclosed his work for the company.

This spring, Guilfoyle arrived in Bulgaria on a private jet provided by Aktor's CEO and urged officials there to do business with the company.

"There is no doubt that this is kind of an official position of the U.S. government," a person familiar with the talks told The Journal.

Robin Brooks, who oversaw the Balkans on the National Security Council under former President Joe Biden, called an ambassador promoting a foreign company "absolutely problematic." Bringing a registered lobbyist into meetings with foreign officials, she said, "calls into question whether the meeting is advancing American interests or advancing some sort of private interest."

Guilfoyle's lawyer, Jesse Binnall, said she has "worked with companies across the energy sector" and that her official meetings are arranged through embassy channels rather than through Marafatsos. Lawyers for Aktor said the company's involvement began before it had any contact with the ambassador.

"I am proud to champion commercial initiatives that advance U.S. interests and create lasting economic opportunity in Greece and Southeastern Europe," Marafatsos said in a statement.

Secretary of State Marco Rubio called Guilfoyle an "incredibly effective advocate for the President's agenda."