(Reuters) - U.S. President Donald Trump is beefing up his legal team with a lawyer who accuses the FBI and U.S. Justice Department of trying to frame Trump with false charges of colluding with Russia during the 2016 election campaign, possibly signaling a more aggressive drive to discredit Special Counsel Robert Mueller.

Washington lawyer Joseph diGenova will join the legal team later this week, according to attorney Jay Sekulow, who also represents Trump. DiGenova, a former U.S. attorney for the District of Columbia, did not respond to requests for comment.

DiGenova has been a vocal proponent on right-wing media of what he calls a “brazen plot” by top Federal Bureau of Investigation and Justice Department officials to clear Hillary Clinton of alleged criminal conduct for storing classified materials on her private email server when she was secretary of state.

According to diGenova, when Clinton lost the 2016 presidential election to Trump, the senior officials, including former FBI Director James Comey, sought to ruin Trump with an investigation into possible collusion between his 2016 campaign and Russia.

“They tried to frame an incoming president with a false Russian conspiracy,” diGenova said in a January interview with the Daily Caller News Foundation. “They plotted to ruin him as a candidate and then destroy him as a president.

DiGenova’s allegations mirror those that Trump himself has frequently made on Twitter and in public comments.

The FBI launched a counter-intelligence investigation in July 2016 into contacts between Trump campaign associates and Russia.

In January 2017, the U.S. intelligence community concluded that the Kremlin conducted an influence operation of fake news, propaganda and other measures that was aimed at swaying the 2016 presidential vote to Trump.

Mueller was appointed special counsel in May 2017 to investigate possible collusion between the Trump campaign and Russia. He also is probing possible obstruction of justice in the firings of Comey and former national security adviser Michael Flynn.

Trump repeatedly has denounced the investigation as a “witch hunt.” Russia denies meddling in the election.

Trump’s lead lawyer, John Dowd, on Saturday called for the Justice Department official overseeing Mueller to bring an end to the investigation.

In a series of tweets over the weekend, Trump accused the FBI leadership of lies and corruption.

The attacks led to warnings by Republicans to Trump on Sunday not to fire Mueller and to let investigators do their jobs.

White House lawyer Ty Cobb in a statement Sunday night said that Trump was “not considering or discussing” Mueller’s firing.

DiGenova and his wife, Victoria Toensing, are partners in the law firm of DiGenova and Toensing.

The firm represents other figures in the Russia probe, including Trump campaign aide Sam Clovis and former Trump legal team spokesman Mark Corallo, who recently spoke with investigators for Mueller.