Two lawmakers claimed Tuesday that the U.S. Secret Service may need to seek outside help to fulfill its mission because agents are leaving the agency faster than they can be replaced.

"USSS simply cannot hire enough personnel to keep pace with historic attrition rates," House Oversight and Government Reform Committee chairman Jason Chaffetz, R-Utah, and ranking Democrat Elijah Cummings of Maryland noted in a Tuesday letter to Secret Service director Joseph Clancy.

"The committee encourages USSS to explore innovative ways to fill this staffing gap-such as detailing qualified law enforcement officials or [administrative, professional, and technical] employees from other agencies-in the short-term while continuing its long-term efforts to develop a zero-based budget and increase hiring and retention," they wrote.

Their letter comes on the heels of a DHS probe that raised questions about the agency's "ability to protect the White House and its occupants." The inquiry was launched after a man succeeded in jumping a fence and entering the White House in 2014.

DHS attempts to bolster the number of special agents have so far failed, because the staffing increases were outstripped by the number of departures over the last two years. If the problem persists, Congress could mandate major overhauls of the Secret Service to ensure that it succeeds at its core "zero-fail mission" of protecting the president.

"Although they may have only indirectly contributed to the events of that night, underlying and continuing resource and management issues are negatively affecting the Uniformed Division and, potentially, its ability to protect the White House and its occupants," the DHS inspector general warned in a report released Tuesday. "In particular, the Uniformed Division is severely understaffed, which has led to inadequate training, fatigue, low morale, and attrition."

The presidential elections are exacerbating the staffing problem by putting an additional strain on the U.S. Secret Service resources, but the larger problem is that employees are leaving faster than the agency can hire special agents.

"Nearly every USSS employee who spoke with the [inspector general] said they had serious concerns regarding UD staffing shortages," the lawmakers observed. "Some employees characterized the agency as 'hemorrhaging' employees."