In her coming book, "Becoming," the former first lady Michelle Obama said she would "never forgive" Donald Trump for promoting the false birther conspiracy, according to excerpts published ahead of the book's release.

During the 2012 US presidential election, Trump advocated the racist conspiracy theory that President Barack Obama was not a US citizen and touted the demonstrably false claim that Obama's birth certificate was not real.

Michelle Obama reportedly called the conspiracy "crazy and mean-spirited" and said it endangered her family.

"What if someone with an unstable mind loaded a gun and drove to Washington?" she wrote, according to The Washington Post. "What if that person went looking for our girls? Donald Trump, with his loud and reckless innuendos, was putting my family's safety at risk."

Michelle Obama's memoir, "Becoming," lays out some of the former first lady's most damning statements on record against President Donald Trump, according to excerpts published ahead of the book's release next week.

In the book, Obama reportedly chastised Trump for promoting what she called the "dangerous" birther conspiracy that she said jeopardized her family's safety.

"The whole [birther] thing was crazy and mean-spirited, of course, its underlying bigotry and xenophobia hardly concealed," Obama wrote, according to a Washington Post review. "But it was also dangerous, deliberately meant to stir up the wingnuts and kooks."

For years, even prior to the 2012 US presidential election, Trump advocated the racist conspiracy theory that questioned the authenticity of President Barack Obama's birth certificate and his citizenship.

"He doesn't have a birth certificate, or if he does, there's something on that certificate that is very bad for him," Trump said during an interview with the Fox News host Laura Ingraham in 2011.

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Obama added that she would "never forgive" Trump for promoting the birther movement.

"What if someone with an unstable mind loaded a gun and drove to Washington?" she said, according to The Post. "What if that person went looking for our girls? Donald Trump, with his loud and reckless innuendos, was putting my family's safety at risk. And for this I'd never forgive him."

Obama released his longform birth certificate in 2011, though it was not until September 2016 when Trump relented and acknowledged Obama was born in the US.

"President Barack Obama was born in the United States," Trump said during a press conference at the time. "Period. Now we all want to get back to making America strong and great again."

He went on, however, to falsely blame his Democratic presidential opponent, Hillary Clinton, for promoting the conspiracy theory.

"Hillary Clinton and her campaign of 2008 started the birther controversy," Trump added. "I finished it. I finished it. You know what I mean."

Obama's memoir, "Becoming," is scheduled for release on Tuesday.