None of Dr. Ben Carson’s advisers have been able to impart “one iota of intelligent information” to the Republican presidential candidate, a top national security expert working on his campaign told The New York Times in a story published Tuesday.

Duane Clarridge, one of Carson’s top advisers on terrorism and national security, told the Times thatCarson has continually struggled with the nuance of foreign policy despite weekly briefing calls and tutoring so “we can make him smart.”

“Nobody has been able to sit down with him and have him get one iota of intelligent information about the Middle East,” Clarridge said in an interview during which he also used an unprintable ethnic slur for the Chinese.

Clarridge, a storied ex-CIA spy once indicted for lying to Congress during the Iran-Contra scandal, now runs a private network of intelligence operatives. His stable of experts on China, Iran, and the Middle East have all briefed Carson over Skype or the phone, he said.

Armstrong Williams, Carson’s top adviser and a frequent spokesman for the campaign, also bemoaned the candidate’s most recent flub on “Fox News Sunday.” Carson couldn’t name any of the countries we would call on for a coalition to defeat the Islamic State, instead saying that he would call “all of the Arab states and even the non-Arab states.”

“He’s been briefed on it so many times,” Williams told the Times. “I guess he just froze.”

The story prompted a stern response from the Carson campaign, which accused the Times of taking “advantage of an elderly gentleman.”

“Mr. Clarridge has incomplete knowledge of the daily, not weekly briefings, that Dr. Carson receives on important national security matters from former military and State Department officials,” Doug Watts, a campaign spokesman, told Business Insider.

Watts also told the site that Clarridge’s “input to Dr. Carson is appreciated but he is clearly not one of Dr. Carson’s top advisors.”

Critics have long questioned the retired neurosurgeon’s policy chops, a weakness brought to the forefront last week after Carson repeatedly said he had “sources” telling him the Chinese military was moving into Syria. The White House flatly denied that claim. Carson also raised eyebrows for a notably meandering answer to a question on foreign policy during Fox Business Network’s Republican presidential debate.

A request for comment from the Carson campaign was not immediately returned.