President Donald Trump has named Stephen Miller as White House chief of staff, moving Susie Wiles to his political operation three days after Republicans lost control of Congress.

Trump said on Friday that Miller, one of his closest advisers across both presidential terms, would start on Monday. He thanked Wiles for her service and said she would shift to the Trump Political Operation. Speaking to reporters, he said Wiles had done a very good job but that moves sometimes had to be made.

Miller has been the main architect of the administration's hardline border and deportation policies, a flashpoint in the midterm campaign. He joined Trump's first election team as an adviser in 2016 and stuck with him after the 2020 defeat. Trump called him one of his most trusted advisers and said he understood politics well.

Wiles submitted her resignation on Thursday night after Republicans lost the House and Senate, according to US officials. Three sources said she quit because of the election losses. She described serving as chief of staff as the honour of a lifetime and said her commitment to Trump and the mission would not change even as her role did. Last month Trump had insisted there was zero chance she would be replaced soon.

Democrats are expected to open investigations into Miller once they take control of both chambers in January. House Democrat Robert Garcia, lined up to lead the Oversight Committee, said he would keep probing what he called misconduct linked to immigration raids. House Minority Leader Hakeem Jeffries denounced the appointment in sharp terms.

The shake up comes as other senior figures leave. Justice Department officials including the head of the national security division and a Florida US attorney have resigned in the wake of the midterm rebuke. Trump was widely expected to reshuffle staff after Democrats netted Senate seats and a clear House majority, with some races still being counted.