Former D.C. Council member Michael Brown in March 2011. (Michael Temchine/For The Washington Post)

Former D.C. Council member Michael A. Brown told supporters Thursday night that he plans to plead guilty to federal charges connected to accepting payments from undercover agents.

Brown made the disclosure in evening conference calls that included close friends and political supporters; the nature of the calls was confirmed by two people who participated.

Federal prosecutors are expected to file charges as early as Friday, government officials said.

Brown, who left the council in January after losing a reelection bid, did not return calls and text messages seeking comment Thursday night.

A spokesman for Ronald C. Machen Jr., the District’s U.S. attorney, declined to comment.

If he is charged, Brown would become the third council member or ex-member to face a criminal complaint for actions while in office. In January 2012, D.C. Council member Harry Thomas Jr. (D-Ward 5) resigned his seat before pleading guilty to stealing $353,000 from city-funded youth programs. Five months later, D.C. Council Chairman Kwame R. Brown (D) resigned before pleading guilty to a felony bank fraud charge. And a grand jury investigation continues into Mayor Vincent C. Gray’s 2010 campaign, which has led to three guilty pleas from campaign figures.

One of the people Brown spoke to Thursday was Robert V. Brannum, a veteran community and political activist who has supported some of Brown’s campaigns. Another person who participated in a call spoke on the condition of anonymity to protect a personal relationship with Brown.

They gave similar accounts of what Brown, 48, told supporters. Many details of the alleged events remain unclear.

Brown, they said, described being approached while in public office by a group of businessmen seeking to become a “certified business enterprise” — a D.C. government program that offers contracting preferences to small, local, woman-owned or minority-owned businesses.

Eligibility is determined by the city’s Department of Local and Small Business Development and can be a slow and onerous process. In the course of their dealings, Brown said, he accepted payments from the businessmen, whom he later discovered were federal agents.

Brown, the son of the late Commerce Secretary and Democratic National Committee Chairman Ronald H. Brown, described the transaction as a “loan arrangement” but said that federal prosecutors saw the matter differently, “as a bribe or gratuity,” Brannum said.

“He argued he did not commit a crime, but he entered into something he should have known better,” Brannum recalled Brown saying. “A trial was risky, with a heavy penalty, and he decided to just take the medicine and move forward.”

The other person said Brown did not use the word “bribe” or “bribery” in describing the charges he would admit to: “He thought he was helping out a group of people who were trying to do the right thing, and he thought he was trying to do the right thing.”

The guilty plea, if entered, would represent the second time Brown has admitted to a federal charge. In 1997, when Brown was 32, he pleaded guilty to a misdemeanor charge connected to an illegal campaign donation scheme.

Brown worked as a lobbyist before entering elective politics in the District. He lost runs for mayor and Ward 4 council member before winning an at-large seat in 2008, dropping his Democratic Party affiliation to take advantage of city laws reserving some at-large seats for other parties.

On the council, he was a supporter of greater city spending on social service programs and positioned himself as a defender of the city’s poorest residents. As an incumbent with a familiar name, he should have been assured of reelection in 2012.

But his campaign was dogged with controversy, none more damaging than the revelation last June that about $114,000 had disappeared from his campaign account. The missing funds played into questions about Brown’s financial history, which included a federal income tax lien, late mortgage payments and missed rent checks.

Brown has blamed the missing campaign money on a theft by his former treasurer, Hakim J. Sutton, whose attorney had said Brown was aware of the withdrawals. No criminal charges have been filed in the case.

Harried by the allegations and facing a motivated and well-financed challenger, Brown faltered. He lost to independent David Grosso by more than 20,000 votes.

Brown attempted a quick comeback, launching a bid in January to fill the at-large seat vacated by Phil Mendelson (D) upon his ascension to chairman. But Brown suddenly left the race in April, three weeks before the election, citing “very important personal and family matters that require my immediate attention.”

The people who spoke to Brown on Thursday said he asked for their support as he enters his plea and faces sentencing.

“I told him I appreciated him taking responsibility for his actions and moving forward,” Brannum said.