 -- In perhaps his fiercest public rebuke of Donald Trump, independent presidential candidate Evan McMullin said Trump’s anti-Muslim rhetoric tramples American ideals, advances terrorists’ apocalyptic strategy, and even poses “a larger threat to our national security than ISIS itself.”

In a speech earlier this year, McMullin, a former CIA officer who launched his campaign for president on Monday, hammered Trump for playing into an ISIS narrative that frames U.S. counter-terrorism efforts as a clash of civilizations between the West and Islam.

“Having spent much of my adult life serving at the CIA and in other national security roles, I know that this rhetoric and those who promote it present a larger threat to our national security than ISIS itself because their rhetoric empowers our enemies while directly attacking our source of power and ability to defeat them,” McMullin said, according to a transcript obtained by ABC News.

“They want this conflict to be a war between the West and Islam. It’s a key part of their apocalyptic vision and strategy,” McMullin said in February at a University of Pennsylvania event. “And so when we have a leading presidential candidate who is doing the work of ISIS for it, we should be very concerned.”

McMullin, a 40-year-old former CIA counter-terror operative who resigned on Monday as chief policy director of the House Republican Conference to launch his presidential bid, is positioning himself as a third-party conservative alternative to Trump.

McMullin articulated a thorough critique of the Republican Party in his February remarks, making the case for a restoration of fiscal conservative principles and a robust American foreign policy that promotes democracy abroad, and called for a more diverse and inclusive party.

He hammered Trump for violating fundamental American ideals like tolerance and respect for “all people, regardless of race, religion, nationality,” and accused him of “attack[ing] Mexicans, Arabs, women, people with disabilities, and others,” according to Jeremiah Keenan, who covered the event for The Statesman of the University of Pennsylvania and provided a transcript of McMullin’s comments.

Since announcing his candidacy, McMullin has continued criticizing the Republican nominee but has yet to repeat his claim that Trump presents a bigger national security threat than ISIS.

He has also gone on offense against Democratic nominee Hillary Clinton, telling ABC News that both she and Trump are “woefully unfit for the responsibilities they seek.”