The FBI’s counterterrorism program cannot adequately protect the nation against another attack by Middle Eastern terrorists, a high-ranking FBI official and recognized whistleblower claimed Wednesday in a rare appearance on Capitol Hill.

Bassem Youssef, in oral and written testimony, decried what he saw as major deficiencies in his own bureau’s counterterrorism operations.

He accused the FBI of needlessly violating the civil liberties of thousands of Americans, misidentifying threats against the United States and repeatedly making “sloppy mistakes."

“My greatest goal is to get the message across that the FBI counterterror division is ill-equipped to handle the terrorism problems we’re facing,” he said before the House Judiciary Subcommittee on Crime, Terrorism and Homeland Security.

Youssef also matter-of-factly declared that the bureau's counterterror operations, including the prestigious International Terrorism Operations Centers, are not adequately staffed. He said many of those who do fill positions in these units have no familiarity with the basics of counterterror investigations, the Arabic language or the cultural nuances of the Middle East they must comprehend in order to be effective.

Supervisor positions in those centers, which cover units that track Al Qaeda, are staffed at only 62 percent of the federally mandated level, he said.

Youssef, currently the chief of the FBI's Communications Analysis Unit, is a known bureau whistleblower whose past statements — and alleged bureau retaliation against him — have triggered investigation by the Department of Justice.

He again ran the risk of backlash Wednesday and expressed some anxiety at the start of his testimony.

"Regardless of what happens to me when I walk into the Hoover building tomorrow, (these concerns) are what I wanted to get across," Youssef told the subcommittee.

The sparsely attended meeting included an appearance at the witness table by Sen. Chuck Grassley, R-Iowa, a longtime FBI critic and advocate of government whistleblowers.

Grassley spoke in support of Youssef and other FBI dissidents, saying, "Underneath all of the good things (in) the FBI, unfortunately, there is a history of abuse, mismanagement and retaliation so strong that it has become part of its organization culture.

"Only a brave few dare to speak out. … When they do speak out, they usually suffer retaliation," he said.

Indeed, Youssef’s testimony Wednesday rattled those on the inside.

FBI Assistant Director John Miller said in a statement Wednesday that the bureau was working hard to staff positions and hire more Arabic-speaking agents, and he warned against reading too much into employee assessments that are “limited in scope.”

“During those years (since the Sept. 11 attacks) … we have disrupted several terrorist plots across the country,” Miller said. “As the men and women of the FBI have accomplished these goals, the threat picture as well as the capability of our adversaries has constantly shifted. We have had to continually develop and shift our strategies to meet those changes.

“It is cynical to write off the work of so many dedicated FBI employees or the accomplishments of the bureau by suggesting that these efforts are failing, especially when they are not.”

And raising eyebrows, Youssef was being aided by a Washington, D.C., public relations firm that appears to have accounts with one or more organizations representing government whistleblowers.

But despite the FBI’s historic disdain for tattletales, sources said Youssef is still widely respected by his colleagues and holds considerable power in the bureau.

He has a long history inside the bureau's counterterrorism structure. According to his biography on the National Whistleblower Center Web site, he administers two warrantless search programs created under the Patriot Act.

Youssef spent time Wednesday criticizing the terrorism operations centers for being “inexcusably understaffed” and filling the gaps with underqualified applicants.

To bolster this assertion, Youssef read aloud the text of two internal FBI e-mails about bureau efforts to fill critical counterterror positions.

One, from April of 2007, revealed that several supervisory agents specializing in training were to be pulled out of the FBI academy in Quantico, Va., and reassigned to counterterror duty. The other, dated March of this year, sought volunteers to fill critical open positions in the counterterror sections.

"But if you talk to counterterrorism executives, they will say they are doing a phenomenal job, " Youssef said. He did not pass out paper copies of the e-mails.

In written testimony, Youssef said the FBI has been unable to adequately hire and train agents fluent in Arabic — or at least knowledgeable about the Middle East and counterterrorism — because of deep-seated discriminatory practices and an ongoing policy that does not reward skills.

Youssef spoke of problems he encountered at the FBI after the Sept. 11 attacks, when he sought work in counterterrorism but was refused because of "confusion" over his name and background.

Youssef recommended a full and independent review of FBI counterterrorism operations by "persons with unquestionable expertise in Middle East terrorism."

FOX News' Ian McCaleb contributed to this report.