Steve Bannon is no fan of House Speaker Paul Ryan (R-Wis) and a new book is revealing just how much the White House chief strategist dislikes the Republican figure.

Bannon reportedly called Ryan "a limp-d**k motherf***er who was born in a petri dish at the Heritage Foundation," according to Devil's Bargain, a new book by Bloomberg Businessweek reporter Joshua Green.

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According to Green, Bannon made the comment in the spring of 2016, when it became clear that Donald Trump had an increasingly likely chance of becoming the GOP nominee. The remark referenced the think tank whose fiscal conservative policies Ryan follows, The Huffington Post reported.

With talks of a contested nomination, some establishment Republicans began to consider Ryan a possible alternative to Trump.

"One fleetingly popular scenario to stop Trump from becoming the nominee was for GOP delegates to coalesce around a white-knight alternative at the party convention in July," Green wrote, adding that Ryan "emerged as the chattering-class favourite".

Green wrote that the notion of Ryan as an alternative "sent Bannon into a panic of his own," leading the then-Breitbart chairman to begin "plotting an all-out war to stop Ryan, of whom he was both fearful and dismissive—sometimes whiten the same sentence."

According to Business Insider, Ryan noted that he would not take his party's nomination should it be given to him. "I do not want, nor will I accept the nomination for our party," he said.

Bannon would go on to lead Trump's campaign and now serves as the White House chief strategist. Fellow Breitbart alumna Julia Hahn, who wrote pieces critical of Ryan, also works at the White House now as a staffer.