NEW YORK (CNN/Money) - The assistant to Martha Stewart's Merrill Lynch stock broker pleaded guilty Wednesday to misdemeanor charges of accepting perks to keep silent about an alleged inside stock tip given to Stewart.

A U.S. Magistrate Judge accepted Douglas Faneuil's plea in New York Wednesday.

Douglas Faneuil, assistant to Martha Stewart's stock broker, pleaded guilty to misdemeanor charges of accepting perks to keep silent. CNNfn's Steve Young reports. Play video (QuickTime, Real or Windows Media)

Faneuil and Peter Bacanovic, Stewart's broker at Merrill Lynch, have been fired, a spokesman for the brokerage firm said Wednesday. Merrill placed both on paid leave in June.

Faneuil was fired after he pleaded guilty. Bacanovic was fired for declining to cooperate with investigators looking at trading activity in the stock of ImClone Systems, Merrill said.

Faneuil arrived at an FBI office in lower Manhattan early Wednesday morning in advance of the hearing, which was scheduled for 10 a.m. ET. He appeared relaxed while walking to the building flanked by two lawyers, who shielded him from questions.

Faneuil was charged with "receiving money or other valuable things as consideration for not informing," according to the formal complaint filed by the U.S. Attorney for the Southern District of New York.

"He accepted responsibility for his conduct and pleaded guilty to a misdemeanor," Faneuil's lawyer, Marc Powers, said Wednesday. "Nine months ago he found himself in a difficult situation. He is a young man with guts and courage to come forward."

In exchange for his plea, Faneuil is expected to testify against Stewart, the CEO of Martha Stewart Living Omnimedia (MSO: down $0.45 to $6.80, Research, Estimates), who is suspected of selling her shares in biotech firm ImClone (IMCL: down $0.39 to $7.23, Research, Estimates) based on inside information, according to previous press reports.

Assistant Merrill broker Doug Faneuil leaves court Wednesday after pleading guilty to a misdemeanor charge. (Photo:CNNfn)

Shares of Martha Stewart Living fell sharply.

Stewart has maintained that she and Bacanovic had an agreed that he would sell her shares if the price dipped below $60 a share, which it did last Dec. 27. But Stewart and Bacanovic have yet to provide investigators with concrete proof that such an order existed.

Bacanovic's lawyer, Richard Strassberg of the firm Goodwin Procter, said: "We are disappointed in Merrill Lynch's decision to terminate Peter Bacanovic's employment. However, we remain confident that when the investigation is completed, Mr. Bacanovic will be fully vindicated of any wrongdoing."

Stewart's friend, ImClone founder and ex-CEO Samuel Waksal, already has been indicted and pleaded not guilty to tipping off family members about the pending FDA rejection and trying to sell his shares before the rejection was publicly disclosed.

The complaint filed against Faneuil says that a Waksal family member asked on Dec. 27 that Faneuil execute a sell order on $2.4 million worth of ImClone stock. Later that morning, Faneuil received a call from Waksal's accountant requesting that he transfer 80,000 shares of Waksal's ImClone stock worth $4.9 million to a family member's account and sell it.

Though the complaint does not disclose names other than Fanueil's and Waksal's, it said that the broker Faneuil works for offered him a part of his commission along with a plane ticket and an extra week's vacation for his silence regarding those requests.

The complaint alleges that the broker, presumably Bacanovic, told another client about Waksal's attempts to sell ImClone shares on Dec. 27 and that that client then sold about 4,000 shares, yielding a $228,000 profit. The client would have lost $45,673 if the client had not sold the shares.

Stewart sold about 4,000 shares of ImClone while on vacation last December, a day before the Food and Drug Administration rejected an application for ImClone's cancer drug, Erbitux. Stewart, whose actions are being investigated by federal prosecutors and a congressional panel, has not been charged and has repeatedly asserted that she has done nothing wrong.

On Dec. 28, the FDA issued its rejection. On Dec. 31, the first day ImClone shares traded following the rejection, the stock dipped 16 percent to $46.46, according to the complaint.

Faneuil did not tell SEC attorneys about Waksal's or Stewart's trades during a Jan. 3 telephone interview, the complaint said, and again failed to disclose what he knew during a second interview with SEC attorneys and an FBI agent on March 7, the complaint said.

However, on June 20, Faneuil voluntarily came forward and told Merrill Lynch officials, and subsequently the SEC and FBI, about the ImClone trades, according to the complaint.

A Waksal spokesman had no comment Wednesday. Stewart spokeswoman Allyn Magrino declined comment.