A combination of file photos show U.S. President Donald Trump in the White House in Washington, DC, U.S. April 9, 2018 and former FBI Director James Comey on Capitol Hill in Washington, U.S., June 8, 2017.

President Donald Trump is considering pulling the national security clearances of top-level former intelligence officials for making what the White House described Monday as "baseless accusations" against him.

Those ex-officials include former CIA Director John Brennan, former FBI Director James Comey, former NSA Director Michael Hayden, former U.S. national security advisor Susan Rice and former FBI Deputy Director Andrew McCabe. Some of them said they no longer have security clearances, however.

All of those federal officials served during the Obama administration, and all have been vocally critical of Trump since leaving their posts in government.

"The president is exploring the mechanisms to remove security clearance because they've politicized, and in some cases monetized, their public service and security clearances," Trump's press secretary, Sarah Huckabee Sanders, told reporters during a press briefing at the White House.

"Making baseless accusations of improper contact with Russia or being influenced by Russia against the president is extremely inappropriate, and the fact that people with security clearances are making these baseless charges provides inappropriate legitimacy to accusations with zero evidence," she added, appearing to read from a prepared statement.

Sanders was responding to a reporter's question about a tweet from Sen. Rand Paul, R-Ky., earlier that day announcing his intention to ask Trump to revoke Brennan's security clearance. Paul had asked on the social media platform whether Brennan was "monetizing" his security clearance, making "millions of dollars divulging secrets to the mainstream media with his attacks" against Trump.

Rand Paul tweet

It was not immediately clear if any prior U.S. president had revoked former intelligence officers' security clearances for similar reasons. But then-President Barack Obama did not strip retired Army Gen. Michael Flynn of his clearance, which had been granted by the Obama administration in 2010 and renewed in 2016, even while Flynn was campaigning for Trump.

Flynn, who was Trump's short-lived national security advisor, has since pleaded guilty to lying to the FBI and opted to cooperate in special counsel Robert Mueller's Russia probe. On the campaign trail, he had on multiple occasions tweeted conspiracy theories about Trump's opponent, Hillary Clinton.

Brennan had offered a particularly scathing review of Trump's performance at a press conference last week in Helsinki, Finland, alongside Russian leader Vladimir Putin. The U.S. president had refused to say whether he believed his own administration's intelligence agencies, which say Russia attacked the 2016 election, versus Putin, who denies any such interference.

The press conference was roundly criticized by politicians of both major parties. But few went as far in excoriating the president as Brennan, who in a tweet shortly following said Trump's performance "exceeds the threshold of 'high crimes & misdemeanors,'" adding, "It was nothing short of treasonous."

Brennan tweet

At the White House briefing on Monday, Sanders pushed back on a reporter's question about whether Trump simply wanted to punish people whose free speech he disliked.

"The president doesn't like the fact that people are politicizing agencies and departments that are specifically meant to not be political and not meant to be monetized off of security clearances," she said.