WASHINGTON >> Attorney General William Barr believes the Russia investigation that shadowed President Donald Trump for the first two years of his administration was started without any basis and amounted to an effort to “sabotage the presidency,” he said in an interview with Fox News Channel that aired today.

Barr offered no support for his assertion that the FBI lacked a basis for opening the investigation and made no mention of the fact that the bureau began its probe after a Trump campaign adviser purported to have early knowledge that Russia had dirt on Democratic opponent Hillary Clinton.

Barr, who has appointed a U.S. Attorney to scrutinize the origins of the Russia probe, said the Justice Department has evidence there was “something far more troubling” than just mistakes during the investigation that was eventually taken over by special counsel Robert Mueller.

“I think the president has every right to be frustrated, because I think what happened to him was one of the greatest travesties in American history,” Barr said in the interview with Fox News Channel’s Laura Ingraham.

The attorney general asserted that the FBI launched its counterintelligence investigation into ties between the Trump campaign and Russia “without any basis.”

“Even more concerning, actually, is what happened after the campaign, a whole pattern of events while he was president,” Barr said. “To sabotage the presidency, and I think that — or at least have the effect of sabotaging the presidency.”

The Justice Department’s inspector general found in a December report that the FBI was justified in opening the investigation to protect against a potential national security threat. It did not find any evidence that the decision to start the probe was motivated by political bias.

Trump and his supporters are counting on different conclusions from the investigation led by John Durham, the U.S. attorney Barr selected to examine the early days of the Russia probe. Durham’s investigation is ongoing, and Barr did not provide any evidence about what Durham has found so far.

Mueller concluded that the Russian government interfered in the 2016 election, but his investigation didn’t find sufficient evidence to establish a criminal conspiracy between Trump’s campaign and Russia. Mueller also examined about a dozen possible instances of obstruction of justice and has pointedly said he could not exonerate the president.

The inspector general’s report identified significant problems with applications for warrants to monitor the communications of former Trump campaign aide Carter Page in 2016 and 2017. Investigators were concerned about Page’s ties to Russia, but never charged him with any wrongdoing.

Inspector General Michael Horowitz has said the FBI failed to follow its own standards for accuracy and completeness in wiretap applications provided to the secretive Foreign Intelligence Surveillance Court.

The report detailed 17 errors and omissions in the application process, including failing to tell the court when questions were raised about the reliability of some of the information it had presented to receive the warrants. Those mistakes prompted internal changes within the FBI and spurred a congressional debate over whether the bureau’s surveillance tools should be reined in.

But Barr said he believes they were more than just mistakes, offering a personal view of the probe, a highly unusual move for a prosecutor during an ongoing investigation.

“My own view is that the evidence shows that we’re not dealing with just mistakes or sloppiness,” he said. “There is something far more troubling here, and we’re going to get to the bottom of it.

The FBI began investigating on July 31, 2016 whether the Trump campaign was conspiring with Russia to sway the outcome of the presidential election.

By that point, Russian hackers had broken into the Clinton campaign and other Democratic email accounts and George Papadopoulos, a Trump campaign adviser, had boasted to a professor that he was aware that Russia had derogatory information on Clinton.

Though Trump and Barr have seized on errors made during the surveillance of Page, the investigation had already been underway for months by the time the first application was filed.