Donald Trump slammed Mitt Romney again on Monday as he continued to seethe from the GOP senator's vote to remove him from office.

The president has been sharply critical of the Utah lawmaker and 2012 Republican presidential nominee since Wednesday evening's Senate vote to acquit Mr Trump on counts of abuse of power and obstruction of Congress. Mr Romney voted with Democrats to convict and remove him on the former charge before voting to acquit on the obstruction article.

"How's Mitt Romney? You keep him. We don't want him," Mr Trump said to Utah Governor Gary Herbert, a Republican, during an event with state chiefs executive at the White House.

Herbert did not respond.

The president's attacks on Mr Romney represent a rare instance of GOP-on-GOP tension during his term, when he has kept just about every member of his party living in fear of a critical tweet or remark that might draw a primary challenge from their right.

Conservatives have been outraged by Mr Romney's decision, which he pinned, in large part, on the oath he took at the Senate impeachment trial's start.

"I swore an oath before God to apply impartial justice. And, as you know, I'm a very religious person. I take that very seriously," an emotional Mr Romney said on the Senate floor before casting the removal vote.

"And so I looked at the evidence in a very unbiased manner and concluded that that the president had done as was alleged -- that he did ask a foreign government to interfere in the election, that he did pressure that government by withholding aid," Mr Romney said. "That's as egregious an assault on the Constitution of our country as I can imagine that a president might make."

The president took several shots at the moderate senator the next day during a wild East Room "celebration" during which he mocked the Utah senator and his other political foes - including his House Democratic accusers - at another surreal White House event.