President Trump accused President Obama of direct involvement in FBI efforts to snoop on his 2016 campaign, according to a new book by his former campaign chief.

It is President Trump’s harshest charge yet regarding his predecessor’s possible ties to the investigations that have bedeviled his administration.

“Personally, I think he knew,” Trump tells Corey Lewandowski in the book “Trump’s Enemies,” out Tuesday. “If the shoe were on the other foot … it would be treason and they’d be locked up for

100 years.”

Official documents on the FBI’s Crossfire Hurricane investigation into Trump’s campaign place Obama in meetings about surveillance of the Republican candidates’ aides, co-author Lewandowski writes, citing unnamed sources who say Obama’s name was then redacted from the still-classified papers.

The charges harken back to Trump’s notorious string of tweets from March 2017, when he vented about the FBI’s probe: “Just found out that Obama had my ‘wires tapped’ in Trump Tower just before the victory,” he wrote. “A NEW LOW!”

The allegations in the book, which was co-authored by another former campaign official, David Bossie, emerge as the clock runs down on congressional probes into FBI and Department of Justice actions in the months before the 2016 election.

House Republicans are just five weeks away from ceding power – and the incoming chairmen of the Judiciary and Intelligence committees, Rep. Jerrold Nadler (D-NY) and Rep. Adam Schiff (D-Calif.) respectively, plan to shut down the GOP probes and launch new ones into the president’s tax returns and business ties.

The book draws from the authors’ 45-minute interview with Trump on Sept. 20, as the midterm elections loomed and the White House was roiled by the publication of an op-ed by an anonymous administration official who claimed to be actively opposing Trump’s agenda from within.

The conversation featured Trump’s surprisingly sunny take on the Mueller investigation.

“I think it makes my base stronger,” he said. “I think the level of love now is far greater than when we won.”

Trump also made a rare admission of error: not firing FBI Director James Comey soon enough.

“In retrospect, I should have fired him the day after I won and announced please get the hell out,” he said.

And he launched into a lengthy evaluation of his impact on the judicial branch.

“When I got here, I had 145” judicial vacancies, Trump said. “The reason is President Obama, for whatever reason, got tired or bored or something.

“That’s a big deal. When I finish, if I go just by a normal attrition rate … it’s possible that I’ll have replaced more than 50% of the judiciary.”

One-sixth of active federal judges are now Trump appointees.

But rather than Obama boredom, it was mainly because Senate Republicans slowed the confirmation of Obama nominees in the final year of his presidency.