The White House told John Bolton, President Trump’s former national security adviser, that his tell-all book about his experience in the White House contains classified information.

The White House's National Security Council's Records Management Division sent a letter to Bolton's attorney last week that said his manuscript "appears to contain significant amounts of classified information."

"It also appears that some of this classified information is at the TOP SECRET level," the letter said. "Under federal law and the nondisclosure agreements your client signed, as a condition for gaining access to classified information, the manuscript may not be published or otherwise disclosed without the deletion of this classified information."

Early Wednesday, Trump attacked Bolton on Twitter and questioned his motives for detailing his alleged conduct toward Ukraine in his forthcoming book, The Room Where It Happened.

Contents of the book were reported by the New York Times after Bolton turned it over to the White House’s National Security Council for review. Bolton’s lawyer has accused the White House of corrupting the vetting process by sharing details of the book with those outside the National Security Council's Records Management Division.

Bolton alleged that Trump made security aid to Ukraine dependent on the country investigating his political rival Joe Biden, undermining the Trump defense team's claim that the freeze of security assistance was not linked to the pressure campaign.

The revelation came amid the Senate impeachment trial and has helped fuel calls for witnesses.