The US State Department has launched an inquiry into claims that its security officials tried to cover up sex-and-drugs charges against diplomats and agents.
Bureau of Diplomatic Security agents are responsible for protecting 275 US embassies as well as the secretary of state - and the bureau last came under fire for the 2012 attack on the US mission in Benghazi, Libya.
Now, in a new blow to the agency's credibility, the State Department's watchdog group has called in outside law enforcement officers to investigate the bureau's procedures, amid claims it tried to hush up allegations of the use of prostitutes by agents and even an underground drugs ring supplying contractors.
An internal memo by the State Department's Inspector General found eight cases in which inquiries into alleged criminal activity by diplomatic security agents or contractors were influenced or halted, CBS television reported.
They included allegations that security agents protecting ex-secretary of state Hillary Clinton "engaged prostitutes while on official trips in foreign countries", CBS said, quoting from the memo, a problem the report says was endemic.
It also revealed details of an alleged "underground drug ring" near the US embassy in Baghdad which was said to supply drugs to contractors working for diplomatic security.
In one case, officials told the inspector general they were told to stop investigating an American ambassador "who held a sensitive diplomatic post and was suspected of patronising prostitutes in a public park", CBS reported.
State Department spokeswoman Jen Psaki did not deny any of the allegations but refused to go into specifics.
"We take allegations of misconduct seriously and we investigate thoroughly. All cases mentioned in the CBS report were thoroughly investigated or are under investigation," she said.
She dismissed the idea the State Department would not hand over for prosecution any of its 70,000 staff if they were found to have engaged in criminal activity. "I can say broadly that the notion that we would not vigorously pursue criminal misconducts in any case is preposterous," she said.
"We've put individuals behind bars for criminal behaviour. There is record of that. Ambassadors would be no exception."
Pskai vowed "any case we would take seriously and we would investigate, and that's exactly what we're doing," but she dismissed the notion that the use of prostitutes was endemic.
"Last year alone, the detail accompanied then-secretary Clinton to 69 countries with more than 10,000 person-nights spent in hotels abroad. So I'm not going to speak to specific cases ... but it is hardly endemic."
The department's Bureau of Diplomatic Security has requested a "review by outside, experienced law enforcement officers" to "make expert assessments about our current procedures".
A former investigator with the Inspector General, Aurelia Fedenisn, told CBS: "We also uncovered several allegations of criminal wrongdoing in cases, some of which never became cases."
Members of the diplomatic security bureau told the Inspector General's investigators to back off, she alleged. "We were very upset. We expect to see influence, but the degree to which that influence existed and how high up it went, was very disturbing."
Congressman Ed Royce, chairman of the House of Representatives Foreign Affairs Committee, said he was appalled and had asked congressional staff to investigate.
"The notion that any or all of the cases contained in news reports would not be investigated thoroughly by the department is unthinkable," Royce said.
Additional reporting by Bloomberg