Those visits were part of an investigative probe into the anti-poverty group - as ACORN staffers were secretly videotaped giving O'Keefe and Giles advice on how to hide illegal sex businesses in low-income housing. ACORN has fired three workers implicated in the films.
Giles, in a post on the Web site Biggovernment.com, said she and O'Keefe had been driven by their belief that "ACORN is corrupt" and are on "a quest for truth unraveling the mystery of organized corruption."
But when the phony pimp and prostitute tag team visited ACORN's local office, on Broad Street near Parrish, on July 24, they were apparently shown the door.
Philadelphia ACORN president Carol Hemingway said in a statement on Monday that "after causing a major disturbance, they were asked to leave the office, and a police report was filed."
Hemingway e-mailed copies of the incident report to the news media. No charges were filed against O'Keefe or Giles, and their visit to the City of Brotherly Love has not been part of a series of reports aired on the Fox News Channel.
ACORN - an anti-poverty group that dates back to 1970s and that has long had an active operation in Philadelphia - has already been under fire because of a series of probes into fraud allegedly committed by workers paid to register new voters.
Now, the undercover videos have raised new questions about ACORN's integrity that are echoing loudly in Washington.
The U.S. Senate voted on Monday to block the Housing and Urban Development Department from providing any new federal aid to the organization, a move that could have larger ramifications.
ACORN, which has received $53 million in tax dollars since 1994, could be unable to win HUD grants for programs that provide help for low-income people seeking mortgages.
The Associated Press contributed to this report.