April 28, 2014 -- The FBI arrested New York Congressman Michael Grimm -- a former FBI agent -- on fraud and perjury charges today and then ripped into him for dishonoring the FBI code.

Grimm, a Republican from New York City's borough of Staten Island, surrendered to the FBI this morning. After taking him into custody FBI Assistant Director George Venizelos issued a scathing assessment of Grimm.

“As a former FBI agent, Representative Grimm should understand the motto: fidelity, bravery, and integrity. Yet he broke our credo at nearly every turn. In this twenty-count indictment, Representative Grimm lived by a new motto: fraud, perjury, and obstruction," Venizelos said.

"We demand the best from our political leaders. Yet today, we again find ourselves expecting and rightfully wanting more. And as citizens of this great nation we rightfully demand it,” the FBI agent said.

Grimm, 44, a former Marine as well as an ex-FBI agent, was indicted on charges of fraud, perjury and obstruction. He pleaded not guilty and was released on a $400,000 bond secured by his house.

He left court proclaiming his innocence.

“We’re going to fight tooth and nail until I am fully exonerated,” Grimm said. He denounced the charges as a “political witch hunt” meant to force him from office.

He worked for the FBI from 1991 to 2006. Much of his time he was assigned to investigate securities fraud, but at one time he was part of the Gambino squad investigating organized crime.

Grimm had previously gained notoriety when he was caught on tape after the State of the Union speech earlier this year threatening to throw a reporter off the Capitol's balcony and said he would "break you in half, like a boy."

On the day of the president's State of the Union the congressman's camp had just learned through channels that a new round of interviews and subpoenas had been authorized in their dormant probe. Those interviews and interrogations were key to what is now the case against Grimm.

A spokesman for the congressman said today, “We are disappointed by the government's decision, but hardly surprised. From the beginning, the government has pursued a politically driven vendetta against Congressman Grimm and not an independent search for the truth. Congressman Grimm asserts his innocence of any wrongdoing."

The statement dismissed any suggestion that Grimm would resign.

"When the dust settles, he will be vindicated. Until then, he will continue to serve his constituents with the same dedication and tenacity that has characterized his lifetime of public service as a Member of Congress, Marine Corps combat veteran, and decorated FBI Special Agent," the statement said.

Grimm was elected as a Tea Party candidate in 2010 and is on the ballot in a bid for reelection later this year. For the past two years, federal prosecutors have been examining Grimm's fund-raising for his 2010 race. Two of his fund-raisers have already been charged.

The probe started with an investigation a health food restaurant he owned on the Upper East Side of Manhattan. He invested in the restaurant after leaving the FBI in 2006.

Grimm is accused of under-reporting the wages and payroll at the Healthalicious health food store he bought in 2006. Grimm concealed more than $1 million in gross receipts, and hundreds of thousands of dollars in employee wages, according to the indictment. Federal prosecutors say he avoided federal and state tax law. This all happened before he was elected, but prosecutors also say he lied under oath about the scheme during a deposition in January 2013, while he was a member of Congress.

The seat is getting a reputation as the "bad boy seat." Grimm was elected to replace Rep. Vito Fossella, a Republican who resigned in 2008 after a drunk driving arrest led to the revelation that he had a secret family.

ABC News' Shushannah Walshe and Josh Margolin contributed to this report