Revenue from tickets issued by the District’s network of traffic cameras has declined dramatically over the past year, potentially throwing the city budget out of balance, the chief financial officer warned Monday.

With less than two days left in the city’s fiscal year, CFO Jeffrey S. DeWitt said in a letter to District officials that revenue from fines and forfeitures may end up more than $70 million under projections if the trends hold — a significant chunk of a $6.3 billion local budget. The bulk of the shortfall comes from fines issued through red-light and speeding cameras, which have been the subject of rancorous public debate as their use has proliferated in recent years.

The city expected to collect $93.7 million through automated traffic enforcement in the fiscal year ending Sept. 30, but as of the end of August, the cameras had generated only $26.1 million, according to preliminary cash reports issued by DeWitt’s office. That is a drop-off of 62 percent from the nearly $70 million the city had collected by that point in 2013.

DeWitt didn’t pinpoint a reason for the lagging revenue, noting only that fine revenue had been “projected to increase because of the rollout of new automated enforcement equipment.”

Doxie McCoy, a spokeswoman for Mayor Vincent C. Gray (D), said in an e-mail that fewer tickets have been issued this year for a variety of reasons, including delays in deploying some new devices, higher speed limits on some streets and more motorists obeying the law.

“And we don’t view any of this as a bad thing,” McCoy said. “As we’ve said all along: the purpose of automated traffic enforcement is to improve public safety and save lives, not to raise money.”

But the implications for the District’s budget are considerable: The city had projected it would collect $156 million in camera revenue in the coming fiscal year. Should final tallies expected in December confirm a precipitous decline this year, officials may have to cut $50 million to $70 million in spending from next year’s budget.

The news prompted D.C. Council Chairman Phil Mendelson (D) to take his fellow city leaders to task for being too dependent on ticket revenue in balancing the District’s budget.

In a statement, Mendelson said the revenue projections “add to the black eye” around the camera program delivered by a recent D.C. inspector general’s report that suggested it was more about filling city coffers than maintaining public safety. He noted that the council tried to lower camera fines in 2012 but “couldn’t reduce the fines as much as we wanted because of the revenues that would be lost.”

“The District’s budget should not be dependent on the fines of speeders,” he said.

Police Chief Cathy L. Lanier, an outspoken defender of camera enforcement, said in a statement that she saw in the new figures proof that the cameras are working: “As I have said many times, we usually see significant reductions in citations issued in the first few months of deployment. This demonstrates that drivers are changing their behavior.”

“Our goal is traffic safety,” she continued. “The fact that infractions are going down is a good thing in my view. Automated traffic enforcement is and always has been about safety. We deploy technology as needed.”

News of the declining fine revenue came on the same day city leaders learned of a more welcome financial development: Two of three Wall Street bond-rating agencies said Monday that they were upgrading the city’s general obligation debt. Standard & Poor’s and Fitch both raised their ratings to the “AA” level, matching the rating previously issued by the third firm, Moody’s.