Mr Brennan, who served as Central Intelligence Agency director between 2013 and 2017, has become an outspoken Trump critic.
She announced that security clearances for other former officials, including James Clapper and Sally Yates, are under review. Asked via email why the statement was initially dated July 26th but not released until mid-August, a White House official said "today is the date of the revocation".
"The President has a a constitutional responsibility to protect classified information and who has access to it and that's what he's doing is fulfilling this responsibility", Sanders said.
"Mr. Brennan has a history that calls into question his objectivity and credibility", Sanders told reporters in her opening remarks at Wednesday's press briefing.
"My principles are worth far more than clearances", he added".
Brennan responded, "It's astounding how often you fail to live up to minimum standards of decency, civility, & probity".
Trump's action against Brennan, critics and nonpartisan experts said, marked an unprecedented politicization of the federal government's security clearance process.
Trump also pointed to Brennan's more recent statement to Congress that the U.S. intelligence community did not make use of the so-called Steele dossier in its January 2017 assessment of Russia's interference in the 2016 United States election.
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The White House announced in the end of July that it was "exploring" the possibility of revoking the security clearances of several former intelligence officials who have criticized Mr. Trump. And they wonder if he will next choose to target those who now work on the investigation, which Trump has called a "witch hunt".
President Trump's statement said Mr Brennan's clearance issue raised wider questions about allowing former officials to keep their security clearances.
"Mr. Brennan's lying and recent conduct, characterized by increasingly frenzied commentary, is wholly inconsistent with access to the Nation's most closely held secrets and facilitates the very aim of our adversaries, which is to sow division and chaos", the statement said. The White House looked into revoking Brennan's clearance after he accused Trump of "treason" for meeting with Russian President Vladimir Putin last month. 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.
Instead, Brennan was appointed Deputy National Security Advisor, a position which did not require Senate confirmation.
Well before Monday night, when Trump lawyer Rudy Giuliani let a small bomb drop on Brennan, there was strong evidence that Brennan had been quarterbacking illegal operations against Trump.
The Russia probe is being led by the Federal Bureau of Investigation, the USA domestic intelligence service.
Brennan, who has briefed Republican and Democratic presidents, could now lose access to classified information - a courtesy usually afforded to former senior officials of all political stripes.
"An enemies list is ugly, undemocratic and un-American".