(CBSNEWS) – Former presidents George W. Bush and George H.W. Bush are offering their harshest public opinions of President Trump yet — including the elder Bush’s description of the current commander-in-chief as a “blowhard.”

Those comments appear in a new book on the father-son duo from historian Mark Updegrove, titled “The Last Republicans.” The former presidents have alluded to their thoughts on Mr. Trump’s leadership before. Last month, George W. Bush said “bigotry seems emboldened” under Mr. Trump. But in Updegrove’s book, set to release Nov. 14, the two men offer their bluntest comments yet. Updegrove spoke with CNN about his book, providing some of the text.

“I don’t like him,” the elder Bush told the author in May 2016 after it was clear Mr. Trump would secure the GOP nomination. “I don’t know much about him, but I know he’s a blowhard. And I’m not too excited about him being a leader.”

George W. Bush was not much softer in his comments about Mr. Trump: “This guy doesn’t know what it means to be president,” he says in the book.

White House press secretary Sarah Sanders responded to the former presidents’ criticisms in the book.

“The American people voted to elect an outsider who is capable of implementing real, positive, and needed change — instead of a lifelong politician beholden to special interests,” Sanders told CBS News. “If they were interested in continuing decades of costly mistakes, another establishment politician more concerned with putting politics over people would have won.”