Four House Republicans on Wednesday accused the nation's largest Muslim advocacy group of trying to "infiltrate" Capitol Hill by placing interns in the offices of lawmakers who handle national security issues.

The four lawmakers, members of the anti-terror caucus, asked for an investigation into the Council on American Islamic Relations after discovering an internal memo noting the group's strategy. They also highlighted a new book by Paul Sperry titled "Muslim Mafia," scheduled for release on Thursday, which claims the group has been actively infiltrating Congress.

Reps. Sue Myrick of North Carolina, Trent Franks of Arizona, Paul Broun of Georgia and John Shadegg of Arizona asked the Internal Revenue Service to determine whether CAIR deserves its nonprofit status. They also are asking their colleagues to review a summary of findings that led the Justice Department to name CAIR as a co-conspirator in a terrorism case.

The internal memo, provided to FOXNews.com, stated that CAIR would "focus on influencing congressmen responsible for policy that directly impacts the American Muslim community."

The memo cited three House committees -- Homeland Security, Intelligence and the Judiciary -- as panels on which lawmakers preside over policy affecting American Muslims.

"We will develop national initiatives such as a lobby day and placing Muslim interns in Congressional offices," the memo read.

Earlier this year the FBI severed its once-close ties with CAIR as evidence mounted of the group's links to a support network for Hamas, which the U.S. has designated a terrorist organization.

"It's frightening to think that an organization with clear-cut ties to terrorism could have a hand in influencing policy -- especially national security policy -- within our government," Myrick said. "The investigations that we're asking for are simple, and I'm hopeful that they will bring to light any and all information regarding the goals of CAIR."

Franks called on CAIR to renounce its ties to terrorist groups and state publicly that it does not support Hamas or the Muslim Brotherhood.

"I take the charges levied against CAIR and laid out in this book very seriously because they affect our national security," Franks said in a statement. "This Congress must be deliberate in taking a strong stance against those groups and organizations that align themselves with terrorists."

"We live in a post-9/11 world where the coincidence of nuclear proliferation and Islamic terrorism pose a very dangerous combination and real threat to America's national security," he said. "That is why it is critical, in light of the well supported documents and information, that the U.S. Congress take this issue seriously."

CAIR decried the call as a "racist" and "insidious" attack on Muslims and mocked the allegations.

"If it wasn't so insidious, it would be laughable," CAIR spokesman Ibrahim Hooper told FOXNews.com. "What are their charges? CAIR seeks political participation of Muslims. I'm shocked."

Hooper said the evidence proves only that the group is trying, like every other minority group, to engage Muslims in the political process.

"Why is it evil when Muslims seek political participation?" he asked.

In the book "Muslim Mafia," a six-month sting appears to link CAIR to an organized crime network made up of more than 100 other Muslim front groups that make up the U.S. Muslim Brotherhood. The book claims the group is bent on destroying Western civilization.

Hooper said Sperry's efforts only proved the group's good intentions.

"The guy spied on us for months, stole documents -- and the most they came up with is CAIR seeks to work with policymakers on Capitol Hill?" Hooper said. 

"I see it as a stamp of approval."