Donald Trump says he is firing the first female director of the National Portrait Gallery, which contained a caption that referenced the attack on the US Capitol that his supporters carried out in early 2021.

The president announced the termination on Friday in a post on his social media platform that accused Sajet – born in Nigeria, raised in Australia and a citizen of the Netherlands – of being “a strong supporter” of diversity initiatives that his administration opposes as well as “highly partisan”. He cited no evidence for either claim.

Legal experts, including Eric Columbus, a former litigator for the January 6 select committee, suggested Trump does not have the power to fire Sajet, since the gallery is part of the Smithsonian, which is not run by the executive branch.

In its collection of portraits of American presidents, the gallery had this text about Trump: “Impeached twice, on charges of abuse of power and incitement of insurrection after supporters attacked the US Capitol on January 6, 2021, he was acquitted by the Senate in both trials. After losing to Joe Biden in 2020, Trump mounted a historic comeback in the 2024 election. He is the only president aside from Grover Cleveland (1837-1908) to have won a nonconsecutive second term.”

Sajet arrived in the US with her family in 1997, held positions at the Philadelphia Museum of Art, the Pennsylvania Academy of the Fine Arts, and the Historical Society of Pennsylvania and was appointed director of the National Portrait Gallery in 2013, according to a Guardian profile of her.

The National Portrait Gallery is an art museum in Washington DC that opened in 1968 and is part of the Smithsonian Institution. It boasts the only complete collection of presidential portraits outside the White House.

After beginning his second presidency in January, Trump issued an executive order directing the removal of “improper, divisive or anti-American ideology” from the institution’s storied museums.

Sajet had said the gallery under her leadership tried “very hard to be even-handed when we talk about people and that’s the key”.

“Everyone has an opinion about American presidents, good, bad and indifferent,” Sajet said. “We hear it all, but generally I think we’ve done pretty well.”