Prince William County officials have embraced a plan to fill an unexpected $5 million budget hole, but one supervisor said Tuesday that the dollars the county plans to use reveal a troubling trend.

Prince William found out late last month that its budget for this year was $5 million short because of a keystroke error in the county budget office. The error occurred when a county staffer inadvertently typed in the wrong year — fiscal 2012 instead of fiscal 2013 — in a code that projects the payroll budget, officials said.

The county’s auditors, the McGladrey firm, have looked into the situation and found no wrongdoing, officials said. The firm’s final report has not yet been released.

Board Chairman Corey A. Stewart (R-At Large) said he cobbled together a solution to fill the shortfall with county staff, including County Executive Melissa S. Peacor. That proposal, which supervisors plan to vote on Aug. 6, includes $2.1 million from the county’s “revenue stabilization fund,” which has approximately $20 million more than the 1 percent the county sets aside to maintain good favor with independent credit agencies, budget officials said.

The total amount in the fund this year is $35 million, said county spokesman Jason Grant.

Stewart’s proposal led Supervisor Peter K. Candland (R-Gainesville) to ask: Why does the county have that kind of money lying around? Other supervisors seemed pleased with the budget solution. Supervisor Frank J. Principi (D-Woodbridge) called it “elegant.”

In a heated and lengthy exchange, Candland and Stewart rekindled the past year’s budget debates, and each accused the other of a failure to live up to conservative principles. Stewart said the county must set aside funds for contingencies, such as the projected shortfall.

Candland, who fought for deeper cuts in the county budget than were adopted, said the fund is evidence of “overtaxing.”

“We need to be prepared,” Stewart said. “Contingencies will happen, and they’re going to happen again. We cannot spend down that reserve, it is not fiscally responsible.”

Candland recalled when supervisors haggled over whether to cut the $30,000 Bluebird bus program, which allows seniors to get around the county. It was spared. The board made other cuts to police and fire staffing and a planned expansion of Minnieville Road, among others. He said that the millions available to deal with the budget error should have been part of the debate over the budget or returned to taxpayers.

“Overtaxing is fiscally irresponsible and that’s what were doing,” Candland said.

County officials said they have already cut the contingency fund in the coming years. By fiscal 2018 it will be 1 percent of the county budget, or a projected $18.8 million, the amount mandated by credit agencies to maintain a AAA rating, officials said. The county’s AAA bond rating was recently reaffirmed, a status that means Prince William can borrow money at lower rates.

Stewart’s proposal to fill the $5 million gap further uses $370,000 realized from savings from its AAA status, according to a memo he sent to fellow supervisors. A renegotiated insurance contract adds another $902,000 to savings; an uptick in development applications saves the county $600,000; and carefully managing vacancies will result in another $1 million in savings to plug the $5 million gap, according to the proposal.

Other supervisors stayed out of the back-and-forth between the two Republicans, and they seemed inclined to support Stewart’s proposal. They praised how county staff had handled the situation.

“A mistake was made,” said Supervisor Martin E. Nohe (R-Coles). “I haven’t heard a single person trying to hide from this problem.”