Salazar was supposed to get a raise so he would make as much as other Cabinet secretaries. Then Vitter said he would block Salazar's salary hike until he approved six new deep-water permits each month to allow exploratory oil drilling in the Gulf of Mexico.
Though the Senate ethics committee on Friday chided Vitter, R-Lo., for undermining public trust but stopped short of charging him with rules violations, because no guidance had been issued on such a tactic.
In a statement Friday, Vitter said the committee had validated his action by dismissing the complaint and that he was glad he had "killed Ken Salazar's salary increase -- he has completely failed us on energy policy."
"And I'll absolutely place a hold on any raise for him in the future," Vitter said.
The ethics committee indicated that might be problematic. Committee Chairman Barbara Boxer, D-Calif., and top Republican Johnny Isakson of Georgia wrote Vitter that "going forward, such actions will be viewed ... as improper conduct reflecting discreditably on the Senate."
The ethics committee's letter said Salazar would have received an additional $19,600 after joining the Cabinet in 2009 if Vitter had not blocked the increase.
The current salary for Cabinet members is $199,700, but Salazar's office said he is limited to the $175,000 Cabinet salary that was in effect in 2005 when he became a U.S. senator.
The Constitution bars members of the House and Senate from appointment to any U.S. office where compensation was increased during the lawmaker's term.
Former President George W. Bush in 2008 signed legislation rolling back the interior secretary's salary so that Salazar could be appointed. His salary was eligible to be increased after he joined the Cabinet had not Vitter blocked the raise.
Vitter sent Salazar a letter last May that when permits reached six per month, "I will end my efforts to block your salary increase."
In a statement, Vitter said this was his way of keeping a "boot on the neck" of the Interior Department.
Vitter wanted the number of permits to reach the level prior to BP's 2010 Deepwater Horizon rig explosion that resulted in 11 deaths and one of the worst environmental disasters in the nation's history. The Obama administration instituted a six-month moratorium on deep-water drilling in the Gulf of Mexico.
"While senators have long used holds on nominations to help persuade administrations to carry out or change policies, tying an incumbent secretary's personal salary directly to his or her performance of a specific official act is different, places a secretary in a precarious and potentially untenable position and undermines a basic principle of government service," the ethics letter said.
"As stated in the Code of Ethics for Government Service, `public office is a public trust.' "
The committee said that if Salazar had caved in to the demand, it would have appeared that his decision was made because of his personal interest in obtaining a raise.
A government watchdog group, Citizens for Responsibility and Ethics in Washington, filed the complaint with the committee, formally the Select Committee on Ethics.
The group's executive director, Melanie Sloan, was critical of the committee's failure to punish Vitter.
"So now senators need guidance to know extortion and bribery violate Senate rules?" she said. "If the ethics committee hasn't issued specific advance guidance, senators can't be held accountable for outrageous conduct? How about if the ethics committee just issues this blanket guidance: Criminal conduct violates the rules."
The Associated Press contributed to this report.