In this file photo taken on February 17, 2020, former National Security adviser John Bolton speaks at Duke University in Durham, North Carolina

John Bolton, who served as Donald Trump's national security advisor, has strongly criticized Sebastian Gorka, who has been nominated by the incoming president to serve as deputy assistant to the president and senior director for counterterrorism. Bolton referred to Gorka as a "con man" and suggested that he should undergo a comprehensive FBI field background investigation.

This statement underscores Bolton's concerns over Gorka's qualifications and background, casting doubt on his suitability for such an important national security role.

John Bolton made his critical remark during a CNN appearance on Friday, just after Donald Trump unveiled a range of new nominations for key positions. Bolton's comment targeted Sebastian Gorka, whom Trump has nominated for the role of deputy assistant to the president and senior director for counterterrorism. Gorka, who previously held the position of deputy assistant to the president for seven months in Trump's first term, from January to August 2017, has been a controversial figure. Bolton's sharp criticism raised questions about Gorka's qualifications for the new position, suggesting that his background warranted further scrutiny through an extensive FBI field investigation.

Speaking to CNN, Bolton said: "Sebastian Gorka is a con man. I wouldn't have him in any U.S. government. Fortunately it's not the highest position he had been mentioned for but I don't think it's going to bode well for counter-terrorism efforts when the senior director is somebody like that.

"This is why obviously everybody is now focusing on the top jobs but the questions of who are the deputy secretaries, who are the undersecretaries, is going to tell us a lot about who is actually running the government."

When asked why he considered Gorka a "con man," Bolton responded, "He needs a full FBI field background investigation about his educational claims and things like that. I think he is a perfect example of someone who owes his position purely to Donald Trump."

Bolton went on to criticize Gorka's relationship with Trump, saying, "He doesn't display loyalty, he displays fealty, and that's what Trump wants. He doesn't want Gorka's opinions, he wants Gorka to say 'yes sir,' and I'm fully confident that's exactly what will happen, no matter what it is Trump says."

Although John Bolton served in Donald Trump's first administration for 17 months, he has become a vocal critic of the former president. In February, Bolton remarked that there would be "celebrations in the Kremlin" if Trump won the November 5 presidential election, reflecting his sharp disapproval of Trump's foreign policy approach and his concerns about the implications of a second term under Trump's leadership.