The government's newest cooperating witness in the Jack Abramoff lobbying scandal, a former congressional aide to Rep. Bob Ney, will testify at the trial of the former top procurement official in the Bush administration, prosecutors revealed Tuesday.

Neil Volz, former chief of staff to the Ohio Republican congressman, pleaded guilty last week in the investigation of influence peddling by Abramoff on Capitol Hill, the Interior Department and at the General Services Administration where David Safavian worked.

Safavian, the ex-chief of staff to the GSA's administrator, is accused of concealing from GSA investigators and a Senate committee his involvement with Abramoff's efforts to acquire GSA-controlled property.

Volz will testify about a suggestion from Safavian for inserting language into legislation that would have conveyed to Abramoff some GSA-controlled property in Maryland, Justice Department prosecutor Peter Zeidenberg said at a pretrial hearing.

The government appears intent on keeping Abramoff off the witness stand in the Safavian case by introducing hundreds of e-mails between the lobbyist and Safavian.

In addition to the Maryland property he wanted for a school, the charges against Safavian say Abramoff wanted to arrange a lease for some Indian tribal clients at the Old Post Office, a downtown Washington landmark.

Safavian's lawyer, Barbara Van Gelder, argued against introducing the Abramoff-Safavian e-mails, saying the government has not demonstrated that the lobbyist and his longtime friend engaged in a conspiracy.

Regarding the e-mails, "what we have at worst is reprehensible conduct, improper use of government resources, but it's not a conspiracy," Van Gelder told U.S. District Court Judge Paul Friedman, who has scheduled jury selection in the case for Monday.

Safavian left the GSA for the White House, where he became administrator of federal procurement policy at the Office of Management and Budget.