Abramoff assisted Zachares in obtaining his committee post. Zachares left Young's staff in 2005. Young's office declined to comment Tuesday.
"Guilty, your honor," Zachares told U.S. District Judge Ellen Segal Huvelle, who had asked what plea he would enter to a single count of conspiracy. He faces a maximum of five years in prison, but under federal sentencing guidelines will probably face two years or less.
After the court appearance, defense attorney Edward MacMahon declined to say whether Young knew what Zachares was doing on behalf of Abramoff.
Zachares agreed to cooperate with the government's continuing investigation and, outside the courthouse, MacMahon reinforced that point.
The former Republican aide is the fifth congressional staffer to plead guilty in the Abramoff scandal, including two former aides to former House Majority Leader Tom DeLay, R-Texas.
Zachares provided information to Abramoff about pending congressional actions on the reorganization of federal agencies into the Homeland Security Department.
Zachares said in court that Abramoff and his lobbying team supplied him with $30,000 worth of tickets to sporting events and concerts on more than 40 occasions in the 18 months from mid-2002 to early 2004.
Zachares accompanied Abramoff and six others, including Rep. Tom Feeney, R-Fla., on a $160,000 golf junket to Scotland in 2003, according to the conspiracy count to which Zachares pleaded guilty.
Feeney's office said the Justice Department has contacted the congressman to request more information and that Feeney is cooperating.
Early this year, Feeney agreed to reimburse the government $5,643 for the Scotland trip.
According to a statement of facts that Zachares signed on March 14, he "falsely reported the cost of transportation, lodging and meals as only $5,643, a figure coordinated with Abramoff to be substantially identical as the figures other attendees, including Representative .3, would report."Representative .3" refers to Feeney. After Tuesday's guilty plea, Feeney's office said only that the congressman "is anxious to discuss this matter at the appropriate time."