Washington (CNN) -- The Bush administration used a White House political office as a "boiler room" to support Republican congressional candidates in violation of federal law, a report released Monday by an independent government watchdog agency concludes.

The findings of the report by the Office of Special Counsel echo those of a 2008 House Oversight Committee investigation, which concluded that the activities of the Office of Political Affairs during the administration of President George W. Bush represented a "gross abuse of the public trust."

The Office of Special Counsel report addresses alleged violations of the Hatch Act, a 1939 law meant to prevent using federal employees and resources in political activities. It forbids most federal employees from engaging in political activity while on duty and forbids the use of federal funds altogether.

The White House political unit, or OPA, has typically been used in an advisory role to help keep the president, appointees and others briefed on political matters, according to the Office of Special Counsel, an independent federal agency responsible for enforcing the Hatch Act.

But the agency's investigators found that the Bush-era political affairs office went well beyond that role. Its functions were so intertwined with those of the GOP that at one point employees of the Republican National Committee were working out of OPA offices.

"OPA employees, particularly during the 2006 midterm election season, methodically coordinated administration support to aid the campaigns of Republican candidates," according to the report.

Investigators found that White House political office employees improperly coordinated travel by high-ranking political appointees, including Cabinet members, particularly in support of Republican members of Congress whom the White House had designated as vulnerable in the 2006 election.

The agency also found that the administration and executive agencies did not always properly categorize such travel as political and failed to get reimbursed by campaigns, as federal law requires.

The investigation also concluded that some 75 political briefings conducted by White House political office staffers were improper because they were held in government offices, during working hours or were conducted by employees who weren't exempt from the Hatch Act prohibition on political activity.

"In 2006, the partisan political activity of OPA staff was not incidental to the functions of the office," the report said. "Instead, the OPA director and deputy director focused the time and energy of OPA staff to help advance the Republican Party's electoral prospects, thereby transforming the office into a setting akin to a political boiler room."

Karl Rove, who as a deputy chief of staff to Bush oversaw the White House's 2006 political strategy, did not return a telephone message seeking comment.

In testimony included in the report, Kenneth Mehlmann, who set up Bush's political affairs office and served as its first director, said the office was "by definition" partisan. He said the office took care to separate official and political functions, going so far as to give OPA staffers a second set of computers, printers, e-mail accounts and telephones for use on partisan work.

The Bush administration is not the only one to run into trouble over the office, a version of which was first organized by President Carter, according to the committee.

Both the special council report and the House Oversight Committee investigation note allegations that President Clinton's political office also coordinated the travel of Cabinet secretaries to aid the electoral prospects of Democratic candidates. Some of those activities may have been paid for with federal funds, the report said. The council also noted concern over the political activities of OPA staffers in the Reagan administration -- during which the office emerged in its current form.

Neither the council report nor the House Oversight Committee investigated the earlier administrations' activities. And it's unclear if anything might come of the current report.

The Office of Special Counsel can only bring administrative charges before a merit board, and because all of the employees in question are out of government, the agency no longer has jurisdiction, spokesman Darshan Sheth said.

Although rare, criminal charges involving such violations are allowable. But Sheth said he was unaware of any plans to forward the allegations to the Justice Department for further investigation.

The agency's report recommends that future administrations prohibit White House political offices from coordinating the travel of political appointees to aid congressional campaigns and forbid OPA employees subject to the Hatch Act from engaging in political activities.

But the recommendations may be a moot point.

The Obama administration last week announced that it is disbanding the White House political office and transferring its functions to the Democratic National Committee.

Spokesman Robert Gibbs called the decision "a matter of duplication and efficiency."