United States President Donald Trump on Wednesday revoked the security access of former Central Intelligence Agency Director John Brennan, BBC reported. White House Press Secretary Sarah Sanders announced Trump’s decision, reading out a statement in which the president cited the former intelligence official’s “erratic conduct and behaviour”.

Sanders also said Brennan’s “lying and recent conduct, characterised by increasingly frenzied commentary, is wholly inconsistent with access to the nation’s most closely held secrets”, The Guardian reported. Later in the day, in an interview to The Wall Street Journal, Trump said he would have revoked Brennan’s clearance last week but did not as he had a hectic schedule.

“This action is part of a broader effort by Mr Trump to suppress freedom of speech and punish critics,” said Brennan, who has been one of the vocal critics of the current US government. “It should gravely worry all Americans, including intelligence professionals, about the cost of speaking out. My principles are worth far more than clearances. I will not relent.”

After last month’s summit between Trump and his Russian counterpart Vladimir Putin in Helsinki, Brennan had said the meeting was “nothing short of treasonous”.

Last year, Brennan said an investigation into possible collusion between officials of the Trump presidential campaign and Russia during the US elections in 2016 had been “well-founded”. Trump has repeatedly denied the claim and called it a “witch hunt”.

Meanwhile, Trump’s lawyer Rudy Giuliani warned Special Counsel Robert Mueller, who is investigating the allegations of collusion, that he would unload on him “like a ton of bricks” if the investigation is not wrapped up by September 7, Bloomberg reported.

“CNN poll shows 66% say Mueller should complete his investigation before the upcoming elections,” Giuliani, the former mayor of New York, tweeted on Wednesday. “DOJ has policy to refrain from investigatory activity in 60 day period before election. DOJ should require Mueller to submit his report before September 7.”