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Conservative columnist George Will says he's changed his party affiliation, and during a speech urged Republicans not to vote for presumptive party nominee Donald Trump.

“This is not my party,” Will reportedly said Friday during a luncheon held by the Federalist Society, a conservative and libertarian organization.

Columnist George Will participates in a discussion in Washington in 2010. Mark Wilson / Getty Images file

Will, a longtime Washington Post columnist, Fox News contributor and former Ronald Reagan campaign worker, said House Speaker Paul Ryan’s endorsement of Trump was one reason he decided to leave the GOP according to PJ Media, a conservative website.

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In an interview after the event in Washington, D.C., Will told PJ Media's Nicholas Ballasy that he had recently registered as an unaffiliated voter in Maryland.

He said Republicans should refrain from supporting the real estate mogul.

“Make sure he loses,” Will said, acknowledging that he thinks it’s too late for the GOP to come up with another candidate but they can "grit their teeth for four years, and then win the White House.”

NBC News reached out to Will for further comment.

In his most recent column, Will similarly wrote that Republicans “can save their party by not aiding its nominee.”

Republicans: Save your party, don’t give to Trump https://t.co/V0DTE4Fg27 — George F. Will (@GeorgeWill) June 23, 2016

“Trump’s campaign has less cash ($1.3 million) than some congressional candidates have, so Republican donors have never been more important than they are at this moment,” he wrote.

Will has been critical of Trump since the early days of his campaign, and Trump has responded on Twitter by calling the Pulitzer Prize-winning columnist “boring” and “biased.” He also called him a "major loser" on MSNBC's "Morning Joe" in May.