Gov. Christie, while serving as U.S. attorney, billed taxpayers for luxury hotels on trips and routinely failed to follow federal travel regulations, according to a report released Monday.

The report, released by the U.S. Department of Justice's inspector general, found that while many U.S. attorneys and their subordinates approved their own travel and expenses, the vast majority complied with the approved government lodging rate.

However, the investigation found, "a small number of U.S. attorneys routinely exceeded the government rate, by large amounts, with insufficient, inaccurate, or no justification."

The report does not name any individuals, but the Associated Press identified Christie as "U.S. Attorney C" in the report, based on a comparison of details in the report and public records of Christie's travel expenses released under the Freedom of Information Act during his campaign for governor.

Christie, who spent recent weeks campaigning for fellow Republicans across the country and has been hailed by conservatives as a possible candidate for national office, declined Monday to respond to the report. His communications office referred reporters to comments he made in 2009, when the campaign of his opponent, then-Gov. Jon S. Corzine, obtained Christie's travel documents.

Christie said at the time that he stayed in more expensive hotels only when cheaper ones were not available.

Christie served as the U.S. attorney in New Jersey from 2002 to 2008. As a candidate for governor and in his first year as governor, he has called for spending cuts and more ethical behavior from public officials.

The report comes a day after Christie talked about his national ambitions in an appearance on NBC's Meet the Press. He ruled out a run for president or vice president in 2012, but said he might be open to a presidential bid in 2016.

Of the 208 individuals who served as U.S. attorneys during the period reviewed by the office of Inspector General Glenn A. Fine, from 2007 to 2009, five "exhibited a noteworthy pattern of exceeding the government rate and whose travel documentation provided insufficient, inaccurate, or no justification for the higher lodging rates."

Federal regulations allow government employees to be reimbursed beyond government rates, which vary according to location, only in four specific circumstances, including lodging at a prearranged place, such as a hotel where a meeting, conference, or training session is held.

According to the report, Christie exceeded the government rate without adequate justification the most often as a percentage of travel. The investigation found that he submitted 23 vouchers including reimbursement for lodging from 2007 to 2009, of which 15, or 65 percent, exceeded the government rate. The inspector general found insufficient justification for 14 of the 15 cases.

Together, the vouchers exceeded the government rate by $2,176. Twelve of the 14 vouchers involved one case.

The U.S. attorney's secretary said she routinely sought the government rate, but that the U.S. attorney would sometimes pick the hotel where he would stay. The secretary factored into her choice of hotel the time of the meeting and the distance from the hotel to the meeting site.

During one stay in Washington, for example, Christie stayed at the Four Seasons Hotel at a cost of $475 per night, more than double the government rate of $233 per night, justifying the cost by explaining that he was scheduled to speak at the hotel early in the morning.

The report also took note of Christie's reimbursements for transportation to and from airports. In Boston, for example, to travel a distance of four miles, he arranged for car service that cost $236 round-trip, instead of a taxi. And in London, car service between the airport and a hotel cost taxpayers $562 for a round trip.

Christie declined to be interviewed by the Inspector General's Office, but provided a letter stating that he was unable to provide "any other specific information" to supplement the travel documentation.

"Most of the justification memoranda that we found simply stated that the government rate was unavailable, but provided no substantiation for this claim," the report says. "In four cases, there was no justification memorandum at all."

The report concludes that deficiencies in Department of Justice travel policies contributed, but did not excuse, the problems that were uncovered.