U.S. Senator Tom Coburn released his final oversight report on the Department of Homeland Security, which has found major problems in the branch.

The report finds that Homeland Security is not successfully executing any of its five main missions.

“Ten years of oversight of the Department of Homeland Security finds that the Department still has a lot of work to do to strengthen our nation’s security,” Coburn explained.  “Congress needs to review the Department’s mission and programs and refocus DHS on national priorities where DHS has a lead responsibility.”

Homeland Security spent $50 billion over the past 11 years on counterterrorism programs, but the Department cannot demonstrate if the nation is more secure as a result.

Coburn also found that 700 miles of the nation’s southern border remain unsecured. The DHS is not effectively administering or enforcing the nation’s immigration laws, while only 3 in 100 illegal immigrants will ever face deportation.

The report also found that the DHS spends more than $700 million annually to lead the federal government’s efforts on cybersecurity, but struggles to protect itself, federal and civilian networks from the most serious cyberattacks.

The Department has spent $170 billion for natural disasters since 2002 because of an increased federal role in which the costs of small storms are declared “major disasters.”

Even with the grim findings, Coburn expressed optimism about the Department’s future if Congress acts swiftly to address the problems in the report.

“I am confident that Secretary Jeh Johnson is leading the Department in the right direction,” Coburn commented.  “One of the biggest challenges that Sec. Johnson and DHS face is Congress and its dysfunctional approach to setting priorities for the Department.  Congress needs to work with the Department to refocus its missions on national priorities and give Secretary Johnson the authority to lead and fix the Department.”

Coburn served his final day as senator. He thanked his fellow members of the Homeland Security and Government Affairs Committee.

Homeland Security spokeswoman Marsha Catron said: "The men and women of the Department of Homeland Security salute Dr. Tom Coburn for his outstanding service in the United States Senate. (But)Dr. Coburn’s report on DHS overlooks much of the concrete and recent progress we have made over the past year to improve homeland security and the manner in which DHS conducts business."

Fox News’ Mike Emanuel and Jason Donner contributed to this report.