Supporters of the probe insist that U.S. officials were acting appropriately and in the public interest by investigating claims over the Trump campaign's engagements with Russian-linked figures.
"But these are two different things", McQuade wrote.
Testifying in front of the Senate Appropriations subcommittee Wednesday morning, Attorney General Bill Barr said he believes spying did occur during the 2016 presidential election against Donald Trump's campaign.
But at a congressional hearing on Capitol Hill on Wednesday morning, Barr said: "I think spying did occur" on the Trump campaign.
In March 2017, Trump accused his predecessor in the White House, Barack Obama, of "wire tapping" the Trump Tower offices in NY before the presidential election in November 2016, claiming the former president had overseen a "Nixon/Watergate"-style intervention".
The letter said that Mueller did not find a criminal conspiracy between Russian Federation and Trump associates in the 2016 campaign, and that Barr did not believe the evidence in the report was sufficient to prove the president had obstructed justice.
The Justice Department's inspector general has been investigating the early days of the FBI's Russian Federation probe, but Barr has said he wants to pull together the different reviews underway and see if there are remaining questions that need to be addressed.
The comments reflect how quickly attention in Washington has flipped from Trump-Russia links to whether the Russia election meddling probe itself acted inappropriately. "Does Trump finally have his Roy Cohn?"
Earlier, Mueller finished his investigation and submitted some 400-page report to Barr.
Mr Trump said: "This was an attempted coup".
He added, "So the Mueller report when they talk about obstruction, we fight back".
'What they did was treason.
Mr. Trump's allies have long argued that Federal Bureau of Investigation and Justice Department officials should have disclosed to the Foreign Intelligence Surveillance Court that Mr. Steele's dossier was indirectly funded by the Democratic party and Hillary Clinton, the 2016 Democratic nominee for President, through a law firm named Perkins Coie.
BRIAN SCHATZ: I think the word spying could cause everybody in the cable news ecosystem to freak out.
'And a lot of this has already been investigated, and a substantial portion of it has been investigated and is being investigated by the Office of Inspector General at the [Justice] Department. "The question is whether it was adequately predicated". "The problem right now he is at a point in time where people are watching him, they have got questions about him", he said. But Trump went a step beyond Attorney General William Barr, accusing the government of committing an illegal, unprecedented act. The FBI had placed confidential informants in direct contact with members of the campaign, according to reports.
Barr, who was nominated to his post by Trump four months ago, told a Senate appropriations subcommittee that though he did not have specific evidence of wrongdoing, "I do have questions about it".