"It should gravely worry all Americans, including intelligence professionals, about the cost of speaking out".
"I call it the rigged witch hunt, [it] is a sham", Mr. Trump said in an interview.
Sanders, responding to reporters' questions, denied that Brennan and others are being singled out because they are critics of Trump.
"If Mr. Trump believes that this is going to lead me to just go away and be quiet, he is very badly mistaken", Brennan said on MSNBC. Spokeswoman Sarah Huckabee Sanders said Brennan, who was Central Intelligence Agency director under President Barack Obama, has been making "unfounded and outrageous allegations" against the administration.
"As part of the review, I am evaluating action with respect to the following individuals: James Clapper, James Comey, Michael Hayden, Sally Yates, Susan Rice, Andrew McCabe, Peter Strzok, Lisa Page, and Bruce Ohr", the statement said. It accuses Brennan of "increasingly frenzied commentary" and says his behavior is "wholly inconsistent with access to the nation's most closely held secrets".
Shortly after Sanders made the announcement, CNN reported that the White House had not consulted Dan Coats, the director of national intelligence, on the decision.
While the White House sought to paint Brennan as a partisan figure, the president has ignited an avalanche of criticism from national security officials across both sides of the aisle.
Former secretary of state John Kerry accused Trump of "putting personal petty politics ahead of patriotism and national security". Comey fired. McCabe fired. "There has been a clear dividing of the political and national security realms within our country".
Utah firefighter killed while fighting Mendocino Complex fire in California
Almost 19,000 acres of the Stanislaus National Forest and about 11,000 acres of Yosemite National Forest also have been razed. After a month of burning, the Ferguson Fire has singed 96,457 acres across three national forests and private land.
Page is the former Federal Bureau of Investigation lawyer who exchanged anti-Trump text messages with Strzok.
The clearances of eight other administration critics are also in jeopardy, as well as one current Department of Justice official's. But Trump did not order a review of the clearance held by former national security adviser Mike Flynn, who was sacked 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 Federal Bureau of Investigation.
Representative Nancy Pelosi, the House Democratic leader, said Mr Trump's move is a "stunning abuse of power".
"Is John Brennan monetizing his security clearance?"
And a spokeswoman for McCabe, Melissa Schwartz, tweeted last month: "Andrew McCabe's security clearance was deactivated when he was terminated, according to what we were told was Federal Bureau of Investigation policy".
The White House has been besieged by a scandal over a former aide's tell-all memoir in recent days and often tries to defuse crises by stoking new controversy.
Trump said Brennan's clearance was revoked due to a pattern of "erratic behavior" and dishonesty.
"This is an Official Enemies List", Bromwich added.