Mitt Romney — who blasted Donald Trump during the Republican primary as a "phony" and a "fraud" — should be "ashamed" for now courting the president-elect for the secretary of State post, said Ken Langone, a GOP supporter and co-founder of Home Depot (HD).

"Romney disgusts me," Langone told CNBC's "Squawk Box" on Friday. "What he did in the last two weeks he ought to be ashamed. Where's the self-respect?"

In March, Romney gave an unprecedented speech eviscerating candidate Trump — just four years after the 2012 GOP presidential nominee accepted Trump's endorsement.

"The horrible things you said about this man [Trump] and now you're willing to go to work [for him]?" asked Langone, who said he had once "loved" Romney, raising "a lot of money" for the former Massachusetts governor's White House bid.

Romney met with Trump twice recently about the possibility of heading the State Department, a position for which Trump loyalist and former New York City Mayor Rudy Giuliani and Senate Foreign Relations Committee Chairman Bob Corker were also being considered.

Pondering Romney's current state of mind, Langone said in exasperation: "Where is the sense of how can I say these things and then have this man [Trump] as my boss."

Romney did not immediately respond to a request for comment.

Before endorsing Trump in the Republican race, Langone had supported New Jersey Gov. Chris Christie and then Ohio Gov. John Kasich.

In CNBC's Friday interview, Langone also said Trump should not make a habit of pressuring companies to keep jobs in the United States, after the deal to keep a Carrier plant open in Indiana.

Langone said he respects Trump for keeping his campaign promise to save American jobs, but warned the U.S. is not a managed economy.

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