Ex-FBI director James Comey is among those who could lose their security clearance in what is being seen by some as a White House crackdown on Donald Trump's critics.

The US president is said to be "exploring the mechanisms" for stripping clearance from Mr Comey, who has been a vocal dissenter since being fired last year.

In an explosive TV interview in April, he said Mr Trump "lies constantly" and was "morally unfit" to be president, prompting a furious rebuke from his former boss.

Now White House press secretary Sarah Huckabee Sanders has revealed that Mr Comey - along with five other officials who served in the Obama administration - could lose their security clearance.

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Among the five are ex-CIA director John Brennan - who in March said Mr Trump would one day become known as "a disgraced demagogue in the dustbin of history" - and one-time national intelligence director James Clapper.


Mr Clapper told CNN the threat was "very, very petty", adding it was an "abuse of the system".

Former national security agency director Michael Hayden, former White House national security adviser Susan Rice and former FBI deputy director Andrew McCabe are the others Ms Sanders said could lose their clearances.

But a spokeswoman for Mr McCabe has said he had already lost his.

Image: Former CIA director John Brennan is a vocal critic of Mr Trump

Melissa Schwartz tweeted: "Andrew McCabe's security clearance was deactivated when he was terminated, according to what we were told was FBI policy.

"You would think the White House would check with the FBI before trying to throw shiny objects to the press corps."

It would normally be standard practice for each of the officials to continue to hold a security clearance so they can review their old files in case they need to be consulted on important matters.

Ms Sanders said they were being considered for having "politicised and in some cases monetised their public service and security clearances" - and "making baseless accusations" against the president.

Image: Mr Trump has faced criticism in the wake of his first summit with Vladimir Putin

Comments by Mr Brennan in which he attacked Mr Trump's controversial summit with Vladimir Putin as "nothing short of treasonous" were singled out for criticism.

"When you're the person that holds the nation's deepest, most sacred secrets and you go out and you make false accusations against the president of the US, he thinks that is something to be very concerned with," Ms Sanders said.

"Making baseless accusations of improper contact with Russia or being influenced by Russia against the president is extremely inappropriate. It provides inappropriate legitimacy to accusations with zero evidence."

When asked during the Monday press briefing whether the president was punishing them because of their criticism of him, Ms Sanders said: "No, I think you are creating your own story there."

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It came as a judge revealed Mr Brennan was one of five people granted immunity to testify in the criminal trial of the president's former campaign chairman Paul Manafort.

The trial - which was due to begin on Wednesday but has been delayed until next week - forms part of special counsel Robert Mueller's investigation into Russia's interference in the 2016 presidential election.

Mr Manafort faces 16 charges, including bank and tax fraud and failure to file reports of foreign financial accounts, which mainly pre-date his work on the Trump campaign team.

The president has been inconsistent on condemning Russia for interference in the election, which Ms Sanders said he acknowledged had occurred but continued to deny that any collusion had taken place.