Mr Brennan said the move by Mr Trump was "designed to send a message to others. that if you dare to speak out against Mr Trump there are way that he can try to hit back at you".
Castro said, "It's a clear abuse of power, and it's a mark of an authoritarian dictator, really, rather than a democratically-elected president of the United States".
Sarah Huckabee Sanders, Trump's press secretary, insisted on Wednesday the White House wasn't targeting only Trump critics.
The president told The Wall Street Journal he holds Brennan largely responsible for the special investigation to determine the extent of Russian meddling in the 2016 presidential election and whether anybody in Trump's orbit was involved.
"There needs to be an official determination made about this, and that, I think, can only be done by the Mueller investigation", Clapper told CNN on Thursday. Brennan, who led the Central Intelligence Agency under Democratic President Barack Obama, on Thursday called Trump's denials "hogwash" and vowed not to be silenced.
Brennan, who served under President Barack Obama and has become a vocal Trump critic, called Trump's claims that he did not collude with Russian Federation "hogwash". Trump says he is reviewing security clearances for nine other individuals, including the eight pictured.
"If, however, Director Brennan's statement is purely political and based on conjecture, the president has full authority to revoke his security clearance as head of the Executive Branch", Burr added.
Brennan is the first former national security official to see his security clearance revoked since the White House announced last month that Trump was considering taking that action against Brennan and other vocal critics.
That directly contradicted a July 2017 statement from Trump Jr. - written with the consultation of the White House - that claimed the meeting had been primarily about adoption.
Other names on that list include former Director of National Intelligence James Clapper, former Deputy FBI Director Andrew McCabe, former FBI Director James Comey, and many others. "I think that they're very duplicitous".
Sen. Mark Warner, the top Democrat on the Senate Intelligence Committee, warns a "dangerous precedent" is being set. 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". John Brennan's issue is that he challenged a thin-skinned president of the United States, and it really portends unsafe things. After Trump's attack this week on former White House aide Omarosa Manigault Newman, Brennan tweeted that the president failed "to live up to minimum standards of decency, civility, and probity".