Former president Barack Obama responded to President Donald Trump’s accusation that Obama ordered the wiretapping of Trump Tower phones while still in office.

“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,” Obama spokesperson Kevin Lewis said in a statement on Saturday. “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.”

Earlier Saturday morning, Trump posted a series of tweets claiming that Obama in October sidestepped a court ruling to wiretap the then-presidential candidate’s phones on a level that was “Nixon/Watergate.” Trump did not include any evidence or links to back up his assertion.

“I’d bet a good lawyer could make a great case out of the fact that President Obama was tapping my phones in October, just prior to Election!” Trump tweeted just before 7 a.m. eastern. “How low has President Obama gone to tapp [sic] my phones during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy!” the president added.

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