Former CIA Director John Brennan said Thursday that President Donald Trump yanked his security clearance because his campaign colluded with the Russians to sway the 2016 election and is now "desperate" to end the special counsel's investigation.

In an opinion piece in The New York Times, Brennan cites press reports and Trump's own goading of Russia during the campaign to find Democrat Hillary Clinton's missing emails.

Trump himself drew a direct connection between the revocation of Brennan's clearance and the Russia probe, telling The Wall Street Journal the investigation is a "sham," and "these people led it!"

"So I think it's something that had to be done," Trump said.

It was a swift departure from the official explanation given by the White House on Wednesday, which cited "the risks" posed by what Trump labelled Brennan's "erratic conduct and behaviour." The president said he was fulfilling his "constitutional responsibility to protect the nation's classified information."

Brennan wrote that Trump's claims of no collusion with Russia are "hogwash" and that the only question remaining is whether the collusion amounts to a "constituted criminally liable conspiracy."

"Trump clearly has become more desperate to protect himself and those close to him, which is why he made the politically motivated decision to revoke my security clearance in an attempt to scare into silence others who might dare to challenge him," he wrote.

Brennan's loss of a security clearance was an unprecedented act of retribution against a vocal critic and politicizes the federal government's security clearance process. Former CIA directors and other top national security officials are typically allowed to keep their clearances, at least for some period, so they can be in a position to advise their successors and to hold certain jobs.

Other senior military officials defended Brennan. William H. McRaven, a retired Navy admiral who oversaw the 2011 raid that killed al-Qaeda leader Osama bin Laden, urged Trump to revoke his security clearance as a gesture of solidarity with the former CIA director.

"I would consider it an honor if you would revoke my security clearance as well, so I can add my name to the list of men and women who have spoken up against your presidency," McRaven wrote in the Washington Post on Thursday.

President Donald Trump confers with Secretary of State Mike Pompeo, left, during a cabinet meeting on Thursday in the White House. Trump said in an interview published Wednesday that the Russia investigation factored into his decision regarding Brennan. (Andrew Harnik/Associated Press)

Trump said Wednesday he is reviewing the security clearances of several other former top intelligence and law enforcement officials, including former FBI Director James Comey and current senior Justice Department official Bruce Ohr.

All are critics of the president or are people whom Trump appears to believe are against him.

Democrats called it an "enemies list," a reference to the Nixon White House, which kept a list of President Richard Nixon's political opponents to be targeted with punitive measures.

Potential diversionary tactic

There was no reference to the Russia probe in a White House statement Wednesday that was read at a press briefing and then sent out to reporters. In the statement, Trump denounced Brennan's criticism and accused Brennan of having "leveraged his status as a former high-ranking official with access to highly sensitive information to make a series of unfounded and outrageous allegations, wild outbursts on the internet and television about this administration."

"Mr. Brennan's lying and recent conduct characterized by increasingly frenzied commentary is wholly inconsistent with access to the nations' most closely held secrets," Trump said.

In the Journal interview, Trump said he was prepared to yank Brennan's clearance last week, but that it was too "hectic." The president, who was on an extended working vacation at his New Jersey golf club last week, has been under fire over accusations of racism by former adviser Omarosa Manigault Newman and his bitter reaction to them. Trump's statement, distributed to reporters, was dated July 26, 2018, suggesting it could have been held and then released when needed to change a damaging subject.

Brennan has been deeply critical of Trump's conduct, calling his performance at a press conference last month with Russian President Vladimir Putin in Finland "nothing short of treasonous."

"While I had deep insight into Russian activities during the 2016 election, I now am aware — thanks to the reporting of an open and free press — of many more of the highly suspicious dalliances of some American citizens with people affiliated with the Russian intelligence services," he wrote in the Times.

Brennan said Wednesday that he had not heard from the CIA or the Office of the Director of National Intelligence that his security clearance was being revoked, but learned it when the White House announced it.

Trump said he is reviewing security clearances for these eight: top row from left, former CIA director Michael Hayden, former FBI director James Comey, former acting FBI director Andrew McCabe and former national security adviser Susan Rice. Bottom row from left: former FBI deputy assistant director Peter Strzok, former FBI lawyer Lisa Page, former deputy attorney general Sally Yates and former National Intelligence Director James Clapper. (Associated Press)

Trump's statement said the Brennan issue raises larger questions about the practice of allowing former officials to maintain their security clearances, and said that those of other officials were under review.

They include Comey; James Clapper, the former director of national intelligence; former CIA Director Michael Hayden; former national security adviser Susan Rice; and Andrew McCabe, who served as Trump's deputy FBI director until he was fired in March.

Also on the list: fired FBI agent Peter Strzok, who was removed from the Russia investigation over anti-Trump text messages; former FBI lawyer Lisa Page, with whom Strzok exchanged messages; and senior Justice Department official Bruce Ohr, whom Trump recently accused on Twitter of "helping disgraced Christopher Steele 'find dirt on Trump."'

Ohr was friends with Steele, the former British intelligence officer commissioned by an American political research firm to explore Trump's alleged ties with the Russian government. He is the only current government employee on the list.

"I don't trust many of those people on that list," Trump told the Journal. "I think that they're very duplicitous. I think they're not good people."

Mixed views from Republicans

At least two of the former officials, Comey and McCabe, do not currently have security clearances, and none of the eight receive intelligence briefings. Trump's concern apparently is that their former status gives special weight to their statements, both to Americans and foreign foes.

Sarah Huckabee Sanders, Trump's press secretary, insisted on Wednesday the White House wasn't targeting only Trump critics.

Democrats, and even some Republicans, lined up to denounce the president's move, with House Minority Leader Nancy Pelosi, Democrat from California., slamming it as a "stunning abuse of power." And California's Adam Schiff, the ranking Democrat on the House intelligence committee, tweeted, "An enemies list is ugly, undemocratic and un-American."

Several Republicans also weighed in, with Sen. Bob Corker, Republican from Tennessee, saying, "Unless there's something tangible that I'm unaware of, it just, as I've said before, feels like a banana republic kind of thing."

Sen. Susan Collins, Republican from Maine, said she saw no grounds for revoking Brennan's security clearance, "unless there is disclosure of classified information, of which I'm unaware."

But at least two other Republicans were in favour of Trump's action.

Ron Johnson of Wisconsin said, "I don't have a problem with it at all."

John Kennedy of Louisiana was more explicit in describing Brennan: "I think I called him a butthead and I meant it."

With files from CBC News