Donald Trump has escalated his feud with Mitt Romney, the only Republican senator to vote for his removal from office – but this time he didn't tweet about the Utah senator or blast him in public.

Instead, Mr Trump and the White house left Mr Romney, their party's 2012 nominee for president, off the list of lawmakers with a seat on a new panel to help get the United States open again amid the coronavirus outbreak.

In fact, all the other 52 Republican senators are listed as members of the group, according to a White House document describing the group.

The president reviewed a list of members before it was finalised, a White House official told CNN.

Since Mr Trump became president, he and Mr Romney have not seen eye-to-eye – though the former Massachusetts governor typically has voted with the president, especially on major legislation.

But their tense relationship turned into a feud when Mr Romney broke party ranks to vote to remove Mr Trump, saying he concluded the president abused his power when he asked Ukraine's leader to investigate Joe Biden, then and now the Democratic frontrunner for president, and his son Hunter Biden.

"The grave question the Constitution tasks senators to answer is whether the president committed an act so extreme and egregious that it rises to the level of a high crime and misdemeanour," Romney said in an emotional February floor speech. "Yes, he did."

"The president asked a foreign government to investigate his political rival. The president withheld vital military funds from that government to press it to do so. The president delayed funds for an American ally at war with Russian invaders," he said. "The president's purpose was personal and political. Accordingly, the president is guilty of an appalling abuse of public trust."

As always, Mr Trump swung back.

"Had failed presidential candidate @MittRomney devoted the same energy and anger to defeating a faltering Barack Obama as he sanctimoniously does to me, he could have won the election," Mr Trump tweeted very early the next morning.

At a National Prayer Breakfast shortly after, Mr Trump went even further.

"I don't like people who use their faith as justification for doing what they know is wrong," Mr Trump claimed, even though the deeply religious Mr Romney made clear he had studied the case and concluded the president was guilty of the House-passed charges.

Later the same day, Mr Trump mocked the senator when addressing Utah's other Republican senator, Mike Lee.