Embarrassed by a prostitution scandal, the Secret Service will assign chaperones on some trips to enforce new rules of conduct that make clear that excessive drinking, entertaining foreigners in their hotel rooms and cavorting in disreputable establishments are no longer tolerated.

The stricter measures, issued by the Secret Service on Friday for agents and employees, apply even when traveling personnel are off duty.

The policies, outlined in a memorandum obtained by The Associated Press, are the agency's latest attempt to respond to the scandal that surfaced as President Barack Obama was headed to a Latin American summit in Cartagena, Colombia, earlier this month.

The embattled Secret Service director, Mark Sullivan, urged agents and other employees to "consider your conduct through the lens of the past several weeks."

Sullivan said the rules "cannot address every situation that our employees will face as we execute our dual-missions throughout the world." He added: "The absence of a specific, published standard of conduct covering an act or behavior does not mean that the act is condoned, is permissible or will not call for -- and result in -- corrective or disciplinary action."

"All employees have a continuing obligation to confront expected abuses or perceived misconduct," Sullivan said.

Ethics classes will be conducted for agency employees next week.

The changes were intended to staunch the embarrassing disclosures since April 13, when a prostitution scandal erupted in Cartagena involving 12 Secret Service agents, officers and supervisors and 12 more enlisted military personnel who were there ahead of Obama's visit to the Summit of the Americas.

But the new policies raised questions about claims that the behavior discovered in Cartagena was an isolated incident: Why would the Secret Service formally issue new regulations covering thousands of employees if such activities were a one-time occurrence?

"It's too bad common-sense policy has to be dictated in this manner," said Sen. Charles Grassley, R-Iowa, a member of the Senate Judiciary Committee. "New conduct rules are necessary to preventing more shenanigans from happening in the future, and whether these are the best, and most cost effective, rules to stop future misconduct remains to be seen."

The rules did not mention prostitutes or strip clubs. But they prohibit employees from allowing foreigners, except hotel staff or foreign law enforcement colleagues, into their hotel rooms. They also ban visits to "nonreputable" establishments, which were not defined. The State Department was expected to brief Secret Service employees on trips about areas and businesses considered off-limits to them.

During trips in which the presidential limousine and other bulletproof vehicles are transported by plane, senior-level chaperones will accompany agents and enforce conduct rules, including one from the agency's Office of Professional Responsibility.

The chairman of the House Homeland Security Committee, Rep. Peter King, R-N.Y., praised the new rules as "very positive steps by the Secret Service to make clear what is expected of every agent and also makes clear what will not be tolerated."

The Secret Service has forced eight employees from their jobs and was seeking to revoke the security clearance of another employee, which would effectively force him to resign. Three others have been cleared of serious wrongdoing. The military was conducting its own, separate investigation but canceled the security clearances of all 12 enlisted personnel.

Homeland Security Secretary Janet Napolitano assured senator this week that the incident in Colombia appeared to be an isolated case, saying she would be surprised if it represented a broader cultural problem. The next day, the Secret Service acknowledged it was investigating whether its employees hired strippers and prostitutes in advance of Obama's visit last year to El Salvador. Prostitution is legal in both Colombia and El Salvador.

"If they are true, the emergence of these anecdotes about past Secret Service misconduct is precisely why our committee will be trying to determine if such behavior is widespread," said Sen. Joe Lieberman, R-Conn., who heads the Senate Homeland Security and Governmental Affairs Committee. The committee has asked Sullivan for information "related to misconduct by agents on assignment," he said.

In a confidential message to senators on Thursday, the Secret Service said its Office of Professional Responsibility had not received complaints about officer behavior in El Salvador but would investigate.

On Capitol Hill, early signs surfaced of eroding support for the Secret Service director. Grassley said Sullivan's job could be secure if the scandal were an isolated incident. "But if it goes much deeper, you know, nothing happens or nothing's changed in Washington if heads don't roll," Grassley said on CBS "This Morning."

The White House said the president remained supportive of Sullivan and confident in the capabilities of the Secret Service.