The resignation of Secret Service Director Julia Pierson on Wednesday after a series of embarrassing flubs that have outraged lawmakers and shocked the White House, has raised concern on the agency's ability to protect the president.

Pierson was appointed last year to overhaul the agency's tarnished reputation after a prostitution scandal in 2012. But after recent events, she was called in for a congressional hearing on Tuesday that only served to underscore the agency's spate of problems and its culture of covering up mistakes.

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Some speculate the Secret Service's troubles such as lack of leadership, low morale and its cover-up culture are rooted in the decision made by President George W. Bush in 2003 to transfer the agency from Treasury to the newly-founded Department of Homeland Security (DHS).

At the DHS, the agency lost its quasi-independence and had to compete for staffing and funds with other security groups.

According to Pierson's testimony, the agency has been operating with 550 personnel less than the optimal level. And despite having gained more clients, the agency's 6,572 full-time personnel has only increased by 66 compared to 2005.

The agency's 2014 annual budget of US$1.58 billion is only up 35 percent in the past 10 years.

Considering that the agency's dual role of presidential protector and financial investigator, this amount is significantly lower compared to the overall DHS budget and U.S. federal spending which has seen an increase of 48 percent and 54 percent  in the same time frame, respectively.

Former Comcast Corp security head Joseph Clancy has been assigned as the interim director for the Secret Service. He retired from the Secret Service in 2011 and was considered for the Director position in 2013.

Some lawmakers say the next leader should be someone outside the Secret Service, which would be a radical shift from previous practice. Pierson had been with the agency for around 30 years before she was named director last year.

On Sept. 19, Omar J. Gonzalez scaled the White House's fence, ran across the lawn, dodged security, entered the White House and was able to set foot inside the East Room just off a stairway leading to the family residence before he was caught by officials. Gonzalez reportedly had a small knife in his pocket.

At the time, agency officials said Gonzalez was apprehended just inside the Portico doors.

But the last straw for lawmakers and President Barack Obama was the disclosure on Tuesday by GOP Rep. Jason Chaffertz of Utah, the Wall Street Journal relayed.

Chaffertz said a private security guard with a criminal record rode on an elevator with Obama while on a visit to the Centers for Disease Control and Prevention in Atlanta on Sept. 16.

White House spokesperson Josh Earnest said they had only learned of this incident on Tuesday, practically just minutes before it was made public.

Tagsjulia pierson, Secret Service, Omar Gonzalez, Barack Obama, White House breach, Department of Homeland Security, Joseph Clancy