FBI staff working on an investigation into Donald Trump's presidential campaign called the President a "loathsome human" and an "idiot" during the election race, newly released texts show.
Peter Strzok, an FBI counterintelligence agent, was removed from Robert Mueller's investigation after a series of politically charged text messages between himself and Lisa Page, an FBI lawyer, were discovered.
The tranche of texts also include derogatory comments about Democratic figures, including presidential candidate Bernie Sanders, but some of the harshest comments are reserved for Mr Trump.
In one exchange in March 2016, Ms Page refers to Mr Trump as a "loathsome human" with Mr Strzok responding, "Yet he may win," later saying, "America will get what the voting public deserves."
In another exchange, in October 2016, Mr Strzok writes to Ms Page: "I am riled up. Trump is an (expletive) idiot, is unable to provide a coherent answer. I CAN'T PULL AWAY. WHAT THE (expletive) HAPPENED TO OUR COUNTRY??!?!"
On the day of the election, he wrote: "OMG THIS IS (expletive) TERRIFYING: A victory by Mr. Trump remains possible..."
Mr Strzok added: "I'm worried about what happens if HRC is elected," using the initials for Democrat candidate Hillary Clinton.
Around 10,000 of the texts exchanged between Mr Strzok and Ms Page, with whom he is alleged to have been having an extramarital affair, were released to officials and leaked to US media outlets.
The messages began in the summer of 2015, soon after the FBI launched its email server investigation into Mrs Clinton, and continued over the next year and a half as the presidential race was in full swing.
They were discovered during a Justice Department probe of the FBI inquiry into Mrs Clinton's use of a private email server and have fuelled Republican calls for a second special counsel to investigate Mr Mueller's operation.
Both Mr Strzok and Ms Page worked on the FBI investigation into potential coordination between Russia and Mr Trump's presidential campaign.
Mr Strzok was heavily involved in the Clinton inquiry and was in the room when she was interviewed by the FBI. He later helped investigate whether the Trump campaign worked with Russia to influence the outcome of the 2016 presidential election.
Mr Trump has also used the text messages as a line of attack after he repeatedly claimed the FBI leadership was politically tainted.
Tainted (no, very dishonest?) FBI “agent’s role in Clinton probe under review.” Led Clinton Email probe. @foxandfriends Clinton money going to wife of another FBI agent in charge.— Donald J. Trump (@realDonaldTrump) December 3, 2017
A spokesman for Mr Mueller has said Mr Strzok was removed from the team as soon as the allegations were brought to the office's attention, and that Ms Page had already returned to the FBI. Mr Strzok has been reassigned within the FBI.
The anti-Trump texts were a focus of a congressional hearing on Wednesday involving Deputy Attorney General Rod Rosenstein, who appointed Mr Mueller as special counsel in May and oversees his team's work.
In a House of Representatives judiciary committee hearing, Republicans called on Mr Rosenstein to assess whether the potential conflicts might wrongfully impact Mr Mueller's investigation.
The texts showed "extreme bias against President Trump, a fact that would be bad enough if it weren’t for the fact that these two individuals were employed as part of the Mueller 'dream team' investigating the very person for whom they were showing disdain," Republican Bob Goodlatte said.
Mr Rosenstein told the hearing he was not aware of any impropriety by Mr Mueller's office and there was no good cause to fire the special counsel.
Democrats, meanwhile, downplayed the significance of the texts messages, saying there was no evidence of bias.
"Peter Strzok did not say anything about Donald Trump that the majority of Americans weren't also thinking at the same time," said the committee's top Democrat, Jerrold Nadler.