Sen. John Ensign has established a legal defense fund to help pay his legal bills in connection with investigations being conducted by the Senate Ethics Committee and the Justice Department into his alleged attempts to cover up his extramarital affair.

In a May 28 filing with the Senate Office of Public Records, the Nevada Republican explains that he is creating the legal defense fund “for the purpose of accepting funds and making expenditures in connection with legal expense incurred … in connection with legal inquiries, including by the Select Committee on Ethics of the United States Senate and the United States Justice Department, involving allegations of violations of the standing rules and standards of the Senate and Federal statutes.”

Ensign established the defense fund with $10 of his own money, which is standard practice for such funds.

The FBI and the ethics committee are separately investigating Ensign’s alleged efforts to cover up an affair with a campaign aide, Cynthia Hampton. She is married to Doug Hampton, who was Ensign’s top personal office aide at the time of the affair. The Hamptons no longer work for Ensign.

Citizens for Responsibility and Ethics in Washington, a watchdog group, and others have accused Ensign of using his office to steer clients to Doug Hampton’s lobbying business in exchange for his silence about the affair. Hampton told the New York Times last fall that Ensign had taken specific steps to assist his lobbying clients and helped circumvent the lobbying ban that applied to Hampton as the Senator’s former employee.

The Justice Department has begun issuing subpoenas in the Ensign case, including requests for documents from the National Republican Senatorial Committee, where the Senator served as chairman for the 2007-08 campaign cycle.

Senators are allowed to establish legal defense funds with the approval of the Ethics Committee to pay for civil or criminal proceedings relating to their official duties.

Contributions to such funds are capped at $10,000 per year for an individual and do not count against contribution limits for campaigns, but lobbyists are prohibited from donating.