New York Rep. Michael Grimm pleaded guilty to a single count of tax fraud Tuesday in Brooklyn federal court.

The guilty plea comes one month after the congressman, a Republican who represents Staten Island, was elected to a third term.

In April, Grimm was named in a 20-count indictment that accused him of under-reporting the payroll and earnings of his Upper East Side restaurant, Healthalicious, which he ran from 2007 to 2010. He pleaded not guilty in federal court and was released on bond.

Prosecutors alleged Grimm employed a number of immigrant workers who did not have legal status to work in the U.S., and paid them in cash -- wages that were not reported to the government. He also allegedly "substantially under-reported" the restaurant's gross receipts, lowering its taxes.

Grimm said at the time he was being wrongly accused but asked House Speaker John Boehner to take him off the House Financial Services Committee until his federal case was resolved.

Asked during an October whether he would resign if found guilty, Grimm responded, "Certainly, if I was not able to serve, then of course I would step aside."

Congressman Grimm says he will continue to get back to work and work hard. Will not resign. A photo posted by Marc Santia (@marcsantia4ny) on Dec 12, 2014 at 10:58am PST

House Minority Leader Nancy Pelosi (D-California) called on Boehner to demand Grimm to step down from office in light of the guilty plea. Other Democrats have echoed Pelosi's call.

"Now that the election is over, Congressman Grimm is finally admitting the truth to his constituents," Pelosi said in a statement Tuesday. "Clearly, Speaker Boehner must insist that Congressman Grimm resign immediately."

Boehner, who has forced out other lawmakers for lesser offenses, doesn't plan to comment on Grimm's situation until the two discuss it, Boehner spokesman Michael Steel said. A felony conviction does not disqualify a person from serving in Congress, other than under the 14th Amendment or for certain treasonous acts.

If he refuses to resign, it would take a rare vote by his fellow lawmakers to expel him from the House. The last member to be expelled was James Traficant, D-Ohio, who was kicked out of Congress in 2002.

Grimm, 44, made headlines in January after telling a NY1 reporter he wanted to throw the journalist off a balcony in the Capitol for asking about the campaign finance inquiry.

An independent advisory office recommended that the House Ethics Committee investigate the balcony incident. The ethics panel deferred its investigation into Grimm while the Justice Department case was ongoing.

If Grimm doesn't resign, the panel is sure to address the case next year.

He is scheduled to be sentenced June 8.