Butch Bowers and Deborah Barberi, two South Carolina lawyers, are no longer on Trump’s team, the source said. The source described the move as a “mutual decision”.

It leaves Trump’s defence team in turmoil as he prepares for a trial starting on Feb 8 to consider an article of impeachment passed by the House of Representatives charging Trump with inciting the Jan 6 storming of the US Capitol by his followers.

“The Democrats’ efforts to impeach a president who has already left office is totally unconstitutional and so bad for our country,” said Trump adviser Jason Miller.

“In fact, 45 senators have already voted that it is unconstitutional. We have done much work, but have not made a final decision on our legal team, which will be made shortly,” Miller said.

A total of 45 Senate Republicans backed a failed effort last Tuesday to halt Trump’s impeachment trial, in a show of party unity that some cited as a clear sign he will not be convicted of inciting insurrection at the Capitol.