Former President Barack Obama was ‘livid’ over Donald Trump’s insane accusation he illegally wiretapped Trump Tower during the 2016 campaign, according to a Wall Street Journal report.

Presidential historian Douglas Brinkley told the Wall Street Journal that Donald Trump is violating the “almost unwritten rule that you treat your predecessor with a degree of grace and decorum.”

“There are these kinds of things that have happened in the past, but nothing to the degree where a sitting president would charge his predecessor with a felony,” Brinkley told the Journal.

Obama camp responded aggressively to Trump’s false assertions saying “A cardinal rule of the Obama Administration was that no White House official ever interfered with any independent investigation led by the Department of Justice,” an Obama spokesperson said. “As part of that practice, neither President Obama nor any White House official ever ordered surveillance on any U.S. citizen. Any suggestion otherwise is simply false.”

Read the full report at the Wall Street Journal.