President Donald Trump has abruptly revoked the security clearance of ex-CIA director John Brennan, an unprecedented act of retribution against a vocally critical former top US official.

Later, in an interview with The Wall Street Journal, Mr Trump drew a direct connection between the Russia investigation and his decision, citing Mr Brennan as among those he held responsible for the investigation.

“I call it the rigged witch hunt, (it) is a sham,” Mr Trump told the Journal, which posted its story on its website on Wednesday night. “And these people led it!”

He added: “So I think it’s something that had to be done.”

That connection was not in a statement issued earlier on Wednesday in which Mr Trump denounced Mr Brennan’s criticism of him and spoke anxiously of “the risks posed by his erratic conduct and behaviour.”

The president said he was fulfilling his “constitutional responsibility to protect the nation’s classified information.”

Mr Trump also threatened to yank the clearances of a handful of individuals, including former top intelligence and law enforcement officials, as well as a current member of the Justice Department.

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

Trump Security Clearance
White House press secretary Sarah Huckabee Sanders announces that President Donald Trump will remove the security clearance from former CIA director John Brennan (Andrew Harnik/AP)

However, Democratic members of Congress said it smacked of an “enemies list” among fellow Americans and the behaviour of leaders in “dictatorships, not democracies”.

Mr Brennan, in a phone interview with MSNBC, called the move an “abuse of power by Mr Trump”.

“I do believe that Mr Trump decided to take this action, as he’s done with others, to try to intimidate and suppress any criticism of him or his administration,” he said.

He later added on Twitter that he would not be deterred from speaking out.

He said: “This action is part of a broader effort by Mr Trump to suppress freedom of speech & punish critics. It should gravely worry all Americans, including intelligence professionals, about the cost of speaking out. My principles are worth far more than clearances. I will not relent.”

Mr Trump’s action, critics and nonpartisan experts said, marked an unprecedented politicisation of the federal government’s security clearance process.

It also was a clear escalation in Mr Trump’s battle with members of the US intelligence community as the investigation into Russia election meddling and possible collusion and obstruction of justice continues.

And it came in the middle of the president’s latest controversy — accusations of racism by former adviser Omarosa Manigault Newman and his bitter reaction to them.

Mr 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. The White House later released a new version without the date.

Mr Trump, his statement read by his press secretary, accused Mr 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 characterised by increasingly frenzied commentary is wholly inconsistent with access to the nations’ most closely held secrets,” Mr Trump said.

In the Journal interview, Mr Trump said he was prepared to yank Mr Brennan’s clearance last week but that it was too “hectic.” The president was on an extended working vacation at his New Jersey golf club last week.

Trump Security Clearances
Former CIA director John Brennan (Pablo Martinez Monsivais/AP)

Mr Brennan has indeed been deeply critical of Mr Trump’s conduct, calling his performance at a press conference last month with Russian president Vladimir Putin in Finland “nothing short of treasonous”.

Mr Brennan continued that criticism on Wednesday. “I’ve seen this type of behaviour and actions on the part of foreign tyrants and despots and autocrats for many, many years during my CIA and national security career. I never, ever thought that I would see it here in the United States,” he said.

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

There is no requirement that a president has to notify top intelligence officials of his plan to revoke a security clearance.

“The president has the ultimate authority to decide who holds a security clearance,” the ODNI said in a statement.

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.

Mr 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 others officials’ were under review.

They include former FBI director James 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 Mr 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 Mr Strzok exchanged messages; and senior Justice Department official Bruce Ohr, whom Mr Trump recently accused on Twitter of “helping disgraced Christopher Steele ‘find dirt on Trump’.”

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

At least two of the former officials, Mr Comey and Mr McCabe, do not currently have security clearances, and none of the eight receive intelligence briefings.

Sarah Huckabee Sanders, Mr Trump’s press secretary, insisted the White House was not targeting only Trump critics.

But Mr Trump did not order a review of the clearance held by former national security adviser Mike Flynn, who was fired from the White House for lying to vice president Mike Pence about his conversations with Russian officials and later pleaded guilty to lying to the FBI.

Democrats, and even some Republicans, lined up to denounce the president’s move, with House Minority Leader Nancy Pelosi slamming it as a “stunning abuse of power”.

Senator Mark Warner of Virginia, the top Democrat on the Senate intelligence committee, warned that a “dangerous precedent” was being set by “politicising the way we guard our national secrets just to punish the president’s critics.”

And California Representative 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 Senator Bob Corker 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.”