Rudy Giuliani fires back at former White House aide who accused him of spreading ‘completely false’ theory A whistleblower complaint led to an impeachment inquiry into Trump's actions.

Rudy Giuliani, President Donald Trump's personal attorney, defended himself Sunday on “This Week with George Stephanopoulos” from accusations lodged by the president's former homeland security adviser that he has trafficked unfounded theories about foreign interference in the 2016 presidential election.

Tom Bossert, the former White House official, took aim at Giuliani earlier on "This Week," calling it a mistake for the president to have hired him in the first place. He also called out Giuliani for repeating a “completely false” theory that Ukraine – not Russia – was responsible for interference in the 2016 election.

“At this point I am deeply frustrated with what [Giuliani] and the legal team is doing and repeating that debunked theory to the president,” Bossert, who is now an ABC contributor, said. “It sticks in his mind when he hears it over and over again.”

Giuliani fired back later in the show, telling Stephanopoulos, “Tom Bossert doesn’t know what he’s talking about … I’m not peddling anything.”

The president’s personal attorney also sought to defend his role in pressing Ukrainians to investigate former Vice President Joe Biden, the fallout from which has led to an impeachment inquiry in Congress.

“Everything I did was to defend my client and I am proud of having uncovered what will turn out to be a massive pay-for-play scheme,” Giuliani told Stephanopoulos.

The "pay-for-play scheme" Giuliani has accused Biden of perpetrating in Ukraine dates back to 2016 and the dismissal of the country’s former prosecutor general, Viktor Shokin. At the time, Biden was leading U.S. policy toward Ukraine with an emphasis on cracking down on corruption.

He called for Shokin to be fired.

At one point, Giuliani waved what he said were several affidavits, including one by Shokin defending himself, which he said verified his claims that Shokin was dismissed as a result of his investigation of Burisma and Hunter Biden.

It was not immediately clear how the documents verified those claims.

Trump and Giuliani have accused Biden of calling for Shokin's dismissal because his office was investigating Burisma, the Ukrainian energy company where Biden’s son, Hunter, had a seat on the board of directors.

"This is not about getting Joe Biden in trouble," Giuliani said. "This is about proving that Donald Trump was framed by the Democrats."

But the assertion that Biden acted to help his son has been undercut by widespread criticism of Shokin from several high-profile international leaders, including members of the European Union and International Monetary Fund, who said Biden's recommendation was well justified.

The IMF threatened to withhold aid to Kiev in early 2016, citing “Ukraine’s slow progress in improving governance and fighting corruption,” according to Christine Lagard, the IMF’s managing director.

Giuliani also sought to undermine a whistleblower complaint, which was filed in August and released publicly last week, that describes the nature of the president's phone call with his Ukrainian counterpart, Volodymyr Zelenskiy, and an apparent effort within the White House to “lock down” records of the conversation.

“The whistleblower says, ‘I don’t have any direct knowledge, I just heard things,’” Giuliani said. “I’m not saying [the whistleblower] was false, I’m saying he could have heard it wrong.”

Stephanopoulos cited several examples from the complaint in which the whistleblower accurately described the content of Trump’s conversation with Zelenskiy as compared to the transcript.

The whistleblower, who has not been identified, claimed that at least a half dozen administration officials had raised concerns that Trump had used “the power of his office to solicit interference from a foreign country in the 2020 U.S. election.”

Democrats have accused the president of using his desire for an investigation into the Bidens as leverage with Zelenskiy, particularly in light of the fact that the White House had, at the time, withheld nearly $400 million in aid to Ukraine.

It was later released.

Giuliani’s name is invoked more than 30 times in the whistleblower’s complaint.

When Stephanopoulos asked Giuliani whether he will cooperate with the House Intelligence Committee, for which Rep. Adam Schiff is the chair, Giuliani said he wouldn't cooperate with Schiff. But when pressed said he would “consider it” if his client, the president, signed off.

"I'm a lawyer. It's his privilege, not mine," he responded. "If he decides that he wants me to testify, of course I'll testify, even though I think Adam Schiff is an illegitimate chairman. He has already prejudged the case."

In his interview on “This Week,” Giuliani sought to clarify the timeline of his conversations with Ukrainians and insisted he did not instigate communications.

“November of 2016, they first came to me,” Giuliani said of the alleged outreach from Ukrainians through the State Department. “The Ukrainians came to me. I didn't go to them.”

The State Department and its chief, Mike Pompeo, have faced scrutiny for their handling of Giuliani’s overtures to the Ukrainians. The former U.S. Special Envoy for Ukraine, Kurt Volker, helped coordinate at least one interaction Giuliani had with an aide to Zelenskiy in Madrid in May, Volker confirmed.

Giuliani has claimed the State Department directed him to act and has said he briefed Volker and the U.S. ambassador to the European Union, Gordon Sondland, after his meetings with Ukrainians.

On Friday, ABC News reported that Volker had resigned from his post with the State Department. House Democrats still plan to interview him next week as part of their impeachment inquiry, according to a congressional aide.

Giuliani planned to speak at a conference in Armenia next week, according to a schedule. But he cancelled after news outlets reported that several Kremlin officials and Russian President Vladimir Putin would also be in attendance.