Barack Obama is reportedly “livid” over Donald Trump’s claim Saturday that the former president wiretapped Trump Tower in the run-up to the 2016 presidential election, according to a report from The Wall Street Journal.

In a Tweet on Saturday, Trump accused Obama of tapping his phones during the run-up to the election, comparing it to McCarthyism — an espionage campaign led by former U.S. Senator Joseph McCarthy against supposed communist infiltration.

Obama spokesperson Kevin Lewis responded to the claims, saying that 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.”

“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,” he continued.

However, sources close to The Wall Street Journal have said that Obama is “livid” over the allegations, and the affair is likely to end the pair’s at best cordial relationship.

The pair have reportedly not spoken since Donald Trump’s inauguration, after which Trump called Obama to thank him for the letter he left him in the White House, but the call went unanswered.

When asked before leaving office whether he would respond to Donald Trump’s tweeting, Obama said he would “examine it when it comes,” should Trump “ask core questions about our values and our ideals.”

Yet despite Obama’s desire to “follow the Bush model” by not commenting on actions taken by the new administration, the former president appears to be fully engaged and aware of developments. Reports this week emerged that Obama is employing a team of over a dozen operatives to “keep tabs” on the Trump administration.

Obama has also been linked to some of the anti-Trump protests taking place across the country in response to the administration’s new agenda. For example, Organizing for Action (OFA), the nonprofit group heavily involved in Obama’s 2012 re-election campaign, recently partnered with the newly-formed Indivisible Project for “online training” on how to create maximum-impact protests.

Following Donald Trump’s first executive order temporarily halting immigration, Obama said that he had been “heartened by the level of engagement taking place in communities around the country.”

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