President Donald Trump lashed out the former director of the Central Intelligence Agency on Twitter Saturday morning.

The commander-in-chief, who is spending the weekend at Camp David, quoted National Rifle Association spokesperson Dan Bongino's appearance on Fox News.

“John Brennan, no single figure in American history has done more to discredit the intelligence community than this liar. Not only is he a liar, he’s a liar about being a liar," Trump quoted Bongino as saying.

“John Brennan, no single figure in American history has done more to discredit the intelligence community than this liar. Not only is he a liar, he’s a liar about being a liar.” Dan Bongino on @foxandfriends — Donald J. Trump (@realDonaldTrump) June 2, 2018

The former CIA director published a column in The Washington Post vowing to continue to speak out against the commander-in-chief, until integrity and decency return to the White House.

"The esteem with which I held the presidency was dealt a serious blow when Donald Trump took office," Brennan wrote. "Mr.â€‡Trump’s lifelong preoccupation with aggrandizing himself seemed to intensify in office, and he quickly leveraged his 1600 Pennsylvania Ave. address and his Twitter handle to burnish his brand and misrepresent reality."

He added that President Trump "has shown highly abnormal behavior by lying routinely to the American people without compunction, intentionally fueling divisions in our country and actively working to degrade the imperfect but critical institutions that serve us."

The White House focus on undermining the investigation by special counsel Robert Mueller was singled out for scorn.

"His strategy is to undercut real, potential and perceived opponents; his focus is to win at all costs, irrespective of truth, ethics, decency and — many would argue — the law," he concluded. "His disparagement of institutions is designed to short-circuit legitimate law enforcement investigations, intelligence assessments and media challenges that threaten his interests. His fear of the special counsel’s work is especially palpable, as is his growing interest in destroying its mandate."

The former intelligence official, who first briefed a president in the Oval Office during the presidency of George H.W. Bush, vowed to continue speaking out until certain conditions have been met.

"I speak out for the simple reason that Mr. Trump is failing to live up to the standards that we should all expect of a president," he explained. "As someone who had the rare privilege of directly serving four presidents, I will continue to speak out loudly and critically until integrity, decency, wisdom — and maybe even some humility — return to the White House."