Even as former Rep. Nick Lampson (D) looks to the future in his challenge to embattled House Majority Leader Tom DeLay (R), he must finish dealing with the past: After overspending his office allowance in the 108th Congress, the Texan must pay back more than $16,000 to the U.S. Treasury.

According to a letter issued by the House Office of Finance and Procurement, a copy of which was obtained by Roll Call, Lampson spent $16,602.46 more than the $1.26 million allotment he received under the Members’ Representational Allowance, the fund provided to House lawmakers to pay for staff, lease office space, purchase office supplies, and travel between the Capitol and their districts, as well as other official expenses.

While Members elected to a new term are typically allowed to roll any debt from the past Congress into their budget for the next one, House regulations hold former Members personally responsible for the payment of any expenses that exceed the funds available in their MRAs.

A spokesman for Lampson attributed the cost overrun to a likely accounting error, calling the incident an “honest mistake.”

“It was a mistake. He’s happy to make up the difference,” said Keir Murray, Lampson’s campaign spokesman. The Democrat announced last week that he would challenge DeLay, who is facing the possibility of another ethics investigation, in Texas’ 22nd district.

According to Murray, Lampson exceeded his budget in January after providing salary bonuses to House staff. Before issuing the bonuses, Murray said, Lampson had verified with the Finance Office that he had adequate funds to pay his staff.

“He was told there was a particular amount of money in the account that was sufficient to cover these bonuses, and it turns out there was a mistake,” Murray said. It is not yet apparent, he added, whether the mistake was made by a member of Lampson’s staff or the Finance Office.

According to the Finance Office letter, shortly before Lampson’s term ended in January, the Congressman approved $36,473 in personnel expenses, as well as $7,934 for voucher reimbursements and “in-house support services,” pushing him over his spending limit.

Lampson has yet to receive a copy of the letter, which is dated April 20 although it appears to have been mailed at a later date, but Murray said he expects to receive it within the next several days, at which time the former lawmaker will pay the bill.

Murray said he does not expect the incident will play any role in the Lampson’s campaign.

“This was an honest mistake and we’re going to clear it up immediately,” Murray said.

While it is not uncommon for Members to overspend their biennial allotments, one House official asserted that Lampson’s spending — which exceeded his actual budget by 1.3 percent — represents a significant error.

“It’s exceedingly rare, and frankly rather irresponsible, for a Member to bust their MRA cap to the extent that Rep. Lampson did, especially in light of all the tools Members have at their disposal to track their accounts,” the official said.

According to the Members’ Congressional Handbook, the House Finance Office issues monthly statements to each Member listing year-to-date expenditures and obligated funds. (Those figures are also compiled periodically and published in the Quarterly Statement of Disbursements.)

In addition, each House office is provided with “Document Direct” software, an accounting program intended for use by an office manager or similar staff member to itemize spending.

According to statistics provided by the National Taxpayers Union, the handful of Members who have exceeded their allowances in recent years have typically spent less than 1 percent, or several hundred dollars, above what is available to them.

“Obviously when the typical MRA is a million dollars or more, a couple hundred either way constitutes a rounding error. But once you get into the thousands, there’s obviously a question of proper bookkeeping involved,” said NTU spokesman Pete Sepp.

He added: “Congress is setting an awfully poor example and a sanctimonious one at that when relatively lax bookkeeping is tolerated in its own halls, even as it makes very draconian reporting laws for the private sector.”

Additionally, Sepp criticized accounting rules that allow House offices to correct quarterly spending reports months after Members have submitted their account information.

“A lawmaker could very well be over [budget] in the fourth quarter of a given year, only to be back under when a gaggle of corrections are issued in the quarter following,” Sepp asserted.

A spokesman for the House Administration Committee, which has jurisdiction over MRAs, declined to comment on the matter.

“We have no comment until issues such as this are fully resolved,” panel spokesman Brian Walsh said.