Grassley: Secret Service party culture must end (CBS News) -- The hard partying culture at the Secret Service cannot continue and nothing changes in Washington if heads do not roll, a top Republican senator charged Friday as the prostitution scandal at the elite law enforcement agency widens. "We've got to get to the bottom of the allegations in order to know whether our national security is being protected and the president is being properly protected," Sen. Charles Grassley said in an interview with "CBS This Morning." In addition to initial revelations about agents using prostitutes in advance of President Obama's recent trip to Colombia, CBS affiliate KIRO-TV reported Thursday that the Secret Service agents went by the vanload to a strip club in El Salvador ahead of Mr. Obama's trip there last year. The Secret Service is looking into that report and some others, including accusations that agency personnel traveling in 2009 with former President Clinton partied at strip clubs on a visit to Buenos Aires, Argentina, and that agents and White House staffers went to a Moscow night club known for its sexually charged atmosphere prior to Mr. Clinton's trip to Russia in 2000. The Iowa Republican said the inspector general of the Homeland Security Department, which oversees the Secret Service, should step up his investigation to find out just how much the partying was part of the agency's culture. If it was just the 12 knuckleheads that were involved, as the president said, then I'd say (Secret Service) director (Mark) Sullivan got no problems. But if it goes much deeper, you know nothing happens -- nothing's changed in Washington if heads don't roll," Grassley said. Asked whose head should roll, Grassley said it is too soon to make that judgment. "We've got to make sure the military people involved, the president's advance people, the communication office of the White House and the Secret Service, from now on into the future, this culture can't persist," Grassley said. To see the Grassley interview, conducted by "CBS This Morning" co-hosts Charlie Rose and Erica Hill, click on the video in the player above.