A bipartisan Senate report released last week found that the acting inspector general of the Department of Homeland Security altered and delayed investigations at the request of senior administration officials. That doesn't just raise concerns about possible corruption at upper levels of the Obama administration. It sounds an alarm about potentially tragic inefficiency in an agency charged with protecting America from terrorist attack.

Inspectors general were established by Congress in 1978 to provide an independent and objective critique of the administration of major government agencies. They are nominated by the president but have an independent responsibility to report to Congress and the public. They are the nation's watchdogs for waste, fraud and abuse in the executive branch.

According to the oversight panel of the Senate Committee on Homeland Security and Government Operations, the acting IG at the Homeland Security Department from 2011 to 2013, Charles K. Edwards, sought to ingratiate himself with senior aides to then-Secretary Janet Napolitano and White House officials in hopes of getting President Obama to nominate him for a permanent appointment. At least three reports by his office were allegedly altered or delayed to avoid embarrassment to the department and the White House.

The Senate investigators reported that on one occasion Mr. Edwards' office was investigating a complaint from Congress that the Immigration and Customs Enforcement (ICE) Agency misinformed Congress and state and local governments about a plan to apprehend criminal aliens. Mr. Edwards' investigators found that it had done so, but unintentionally.

According to the Senate report, a senior Homeland Security official asked Mr. Edwards to delay the report until after the director of ICE testified before a Congressional oversight committee - and he complied, saving the agency head from embarrassing questions.

The report also said that on another occasion Mr. Edwards agreed with a suggestion from one of Secretary Napolitano's top aides to restrict access to a critical report on the Transportation Security Agency's advanced image screening technology by giving it an unnecessarily high-security classification. That meant members of Congress could only view the report if they went to a special secure facility at the Capitol.

But the most serious allegation against Mr. Edwards was that he suppressed information reflecting badly on the Secret Service and a White House official. That evidence emerged during an IG investigation of the hiring of prostitutes by Secret Service agents in Bogota, Colombia, as they prepared for a presidential visit in 2012. Whistleblowers told the Senate panel Mr. Edwards ordered them to delete the information. However, Mr. Edwards and Homeland Security refused to supply emails related to this report, so the panel could not reach a conclusion on the charges.

Especially troubling is the fact that Mr. Edwards suspended three employees who protested against the changes - including his general counsel. The federal office that reviews whistleblower complaints said Mr. Edwards inappropriately retaliated against the general counsel.

The office of former Homeland Security Secretary Napolitano, now head of the University of California system, issued a statement last week saying, "Neither Secretary Napolitano nor her staff ordered that anything be deleted in the Inspector General's investigative report [on the Secret Service.] Any suggestion to the contrary is false."

That statement, though, did not address efforts by Ms. Napolitano's staff to control other IG reports in violation of at least the spirit of the law.

Acting IG Edwards appears to have first come the attention of Senate investigators because he hired his wife in apparent violation of federal rules. That investigation soon broadened into one of the most damning revelations of lying to and misleading Congress and the public in recent memory. Yet Mr. Edwards continued to work for Homeland Security in another capacity. He was put on administrative leave Thursday.

Now Congress must work to get the full truth about how far administration officials went to cover up shortcomings in the Department of Homeland Security.