Copies of the book “Fire and Fury: Inside the Trump White House” by Michael Wolff are seen at a Washington bookstore. (Carlos Barria/Reuters)

The publisher of a critical book that President Trump has sought to block sent a defiant letter to Trump’s lawyer on Monday, saying the company has no plans to withdraw it or apologize as the controversy surrounding it continues to fuel sales.

“My clients do not intend to cease publication, no [retraction] will occur and no apology is warranted,” wrote Elizabeth A. McNamara, an attorney for Henry Holt & Co., the publisher of “Fire and Fury: Inside the Trump White House” by Michael Wolff.

Trump’s attorney Charles Harder sought last week to stop publication of the behind-the-scenes book, whose revelations prompted Trump to denounce Stephen K. Bannon, his former chief strategist. Bannon told Wolff that it was “treasonous” for Trump’s son Don Jr. and son-in-law, Jared Kushner, to meet with a Russian lawyer they believed possessed damaging information about Hillary Clinton during the 2016 campaign.

Harder threatened legal action, including a libel lawsuit, if the publisher failed to “immediately cease and desist from any further publication, release or dissemination of the book” or excerpts and summaries of its contents. Trump’s representative also accused Bannon of breaching a confidentiality agreement by giving Wolff interviews.

The publisher responded last week by speeding up the book’s publication date by several days and expanding its press run.

“We’re commencing to sell as many books as we can,” said John Sargent, chief executive of Henry Holt’s parent company, MacMillan Publishers USA, in an interview Monday. “We have multiple printings at multiple printers now and all of our suppliers are doing a remarkable job of getting books into the marketplace. They all realize the importance of this book as a commercial success, but they also recognize the huge importance of reading a book the government is trying to stop.”

Sargent was almost gleeful about the controversy whipped up by Trump and White House officials, saying that the publicity it has generated has propelled sales. The publisher now has orders for more than a million hardcover copies, making it the fastest-selling nonfiction book in Henry Holt’s 151-year history, he said.

Its sales prospects are so strong that Holt has no plans at the moment to publish a paperback edition; Sargent said he expected the hardcover version to sell well for the next two years.

The White House and Trump have disputed Wolff’s characterization of the president as mentally unfit for office. Trump has tweeted that he is, “like, really smart” and even “a very stable genius.”

McNamara, the publisher’s attorney, wrote in her letter to Harder that “we have no reason to doubt . . . that Mr. Wolff’s book is an accurate report on events of vital public importance. Mr. Trump is the President of the United States, with the ‘bully pulpit’ at his disposal. To the extent he disputes any statement in the book, he has the largest platform in the world to challenge it.”

She noted that any lawsuit filed against the publisher would open Trump up to discovery that could reveal information that Trump has declined to disclose.

“Should you pursue litigation against Henry Holt or Mr. Wolff, we are quite confident that documents related to the contents of the book in the possession of President Trump, his family members, his businesses, his campaign, and his administration will prove particularly relevant to our defense,” she wrote.

Trump has a long history of threatening legal action against news organizations that published articles that displeased him in some way. The list includes The Washington Post, the New York Times, the Associated Press, Rolling Stone, NBC News, USA Today and the Village Voice, among others. In each case, he didn’t follow up. Trump did sue a journalist, author Tim O’Brien, over a few lines in a book O’Brien wrote in 2005. Trump claimed O’Brien had libeled him by understating his net worth. The suit was dismissed by a superior court judge; an appeals court upheld the decision.