A former employee of the D.C. businessman at the center of a sweeping political corruption investigation was charged Thursday with violating campaign finance laws.

Federal prosecutors accused Lee A. Calhoun — a frequent contributor to District, Maryland and federal campaigns — of hiding the source of campaign contributions made by his former longtime boss, Jeffrey E. Thompson.

Thompson is the alleged financier of a secret effort to back the mayoral campaign of Vincent C. Gray (D) as well as “straw donor” schemes such as the one Calhoun is said to have participated in.

Calhoun’s attorney, Edward B. MacMahon, said his client would plead guilty to the misdemeanor charge, which carries a maximum sentence of one year in prison.

“He’s agreed to cooperate with the government in its ongoing investigation of campaign finance violations,” MacMahon said.

D.C. corruption scandals: A look at the investigations and where they stand.

The plea represents the first time prosecutors have filed a charge reaching into Thompson’s erstwhile businesses and his vast political fundraising network. In July, public relations consultant Jeanne Clarke Harris admitted to helping Thompson orchestrate straw donations as well as a $653,000 “shadow campaign” — expenditures to benefit Gray that were never reported as required by law. The mayor has denied any wrongdoing.

The charge comes just days after former D.C. Council member Michael A. Brown pleaded guilty to accepting $55,000 in bribes. Brown also admitted to accepting illegal donations that people close to the case said came from Thompson. Brown is continuing to cooperate with prosecutors.

Calhoun is among numerous employees of the former Thompson, Cobb, Bazilio & Associates who donated to political candidates, often via checks written on the same day.

The two-page charging document filed in the District’s federal court Thursday provides a snapshot of Calhoun’s activities, which will be detailed in court next week when a plea agreement is expected to be filed.

Prosecutors accused Calhoun of “causing contributions to be made in the name of others” in 2011, donating to an unidentified House of Representatives campaign when he allegedly knew that the contributions were actually being made by “Executive A.”

Court documents do not identify Executive A, but the description matches Thompson, who was the accounting firm’s majority owner, chairman and chief executive at the time.

Thompson sold his majority stake in the firm in July; it is now named Bazilio Cobb Associates. Calhoun remains a principal there.

Calhoun has, since 2001, donated nearly $100,000 to 65 different campaigns and political committees, according to District, Maryland and federal campaign finance records. The only House campaign he donated to in 2011 was that of Donna M. Christensen, the Democratic delegate from the U.S. Virgin Islands, according to federal campaign finance records.

Calhoun and his wife are each listed as donating $2,300 on June 3, 2011. Besides the Calhouns, Thompson and 10 other employees or partners of the firm also donated at least $2,300 to Christensen on the same day.

Thompson, a native Jamaican, has been active in the Caribbean community in Washington; he has donated to a local Caribbean American PAC, and his firm worked pro bono for Jamaican Women of Washington.

Thompson’s attorney, Brendan V. Sullivan Jr., has a policy of not commenting on pending matters.

Nikita Stewart contributed to this report.