John C. Albaugh, who worked for Rep. Ernest J. Istook Jr., R-Okla., until 2006, pleaded guilty to conspiracy to commit honest services wire fraud in U.S. District Court and faces up to five years in prison, a $250,000 fine and supervised release, the department said in a news release.

Albaugh admitted that from March 2002 until May 2004, he accepted more than $4,000 worth of sporting event and concert tickets, and meals, as well as the use of suites at professional sporting events from Abramoff's colleagues, his lobbying firm and their clients. In return, he agreed to act on their behalf. Albaugh didn't disclose the gifts on his required annual financial disclosure form.

The investigation into the activities of Abramoff and his associates has produced 13 guilty pleas by lobbyists and public officials, and the conviction of another public official, the department said.

Abramoff is serving a six-year term in a federal prison in Maryland for fraud after pleading guilty in a casino boat gambling scheme. He is awaiting sentencing for corruption involving government officials and their staff members.