CNN 's Jim Acosta , Ted Barrett , Adriana Hauser and Joe Johns contributed to this report . Sen. watchdog head denies allegation he hired prostitutes . Senate Ethics Committee group that surfaced allegations now questions tipster 's credibility . Tipster ` ` watchdog head wo n't talk directly to investigators , Peter Williams '' says . Watchdog wo n't confirm whether it is investigating .
Sen. watchdog head denies allegation he hired prostitutes . Senate Ethics Committee group that surfaced allegations now questions tipster 's credibility . Tipster `` watchdog head wo n't talk directly to investigators , Peter Williams '' says . Watchdog wo n't confirm whether it is investigating .