A House of Representatives ethics panel on Thursday launched an investigation into the scandal in which lurid sexual messages were allegedly sent by Mr Foley to teenaged pages in Congress.
Republican Dennis Hastert apologised for the handling of the matter but again rejected calls for his own resignation as questions were asked about when the Republican leadership found out about Mr Foley's behaviour and why it did not act earlier.
The Republicans in a desperate battle to keep control of Congress in November 7 elections.
The House investigation comes on top of criminal investigations launched by the Federal Bureau of Investigation (FBI), Justice Department and the authorities in Florida, where Mr Foley comes from.
The bipartsian House Ethics Committee inquiry said it had ordered about four dozen subpoenas for individuals and documents, including direct testimony from Congress members.
The ethics committee chairman Representative Richard 'Doc' Hastings, a Republican, said all of Congress had been "appalled" at reports of the suggestive messages sent by Mr Foley to the teenaged boy.
Representative Howard Berman, the ranking Democrat on the committee, said lawmakers wanted the investigation finished in "weeks".
The committee will investigate Mr Foley's sexual overtures to teenage male aides over several years, and whether Republican leaders properly handled the ensuing scandal, House Ethics committee chairman Doc Bremer said.
"Like all Americans, we are both appalled at the revelations of highly improper communication between former Representative Mark Foley and a young man who came to know Mr Foley while working here in the Capitol as a congressional page," Mr Hastings said.
"Simply put, the American people, and especially the parents of all current and former pages, are entitled to know this situation was handled. And we are determined to answer their questions," he said.
House Speaker Hastert, who has come under fire for his handling of the scandal, promised to fully cooperate with the investigation and admitted errors had been made handling the scandal.
"I'm deeply sorry this has happened," he said at a press conference on Thursday at his stronghold in Illinois.
"The bottom line is that we're taking responsibility, because ultimately, as someone has said in Washington before, 'the buck stops here'."
He added: "Any person who is found guilty of improper conduct involving sexual contact or communication with a page should immediately resign, be fired, or be subjected to a vote of expulsion," Mr Hastert said.
"Anyone who had knowledge of the vile instant messages should have turned them over immediately so that our House pages could be protected," he added.
He said he has asked the committee also draw up guidelines for future communication and contact between lawmakers and pages.
Mr Hastert also announced that the House had established a phone "tip line" which pages can phone to report any information they might have about the Foley scandal, or any complaints about the page program.
Mr Hastert insisted he had only learned of the "explicit language" in the messages last Friday and the Republican party had acted immediately. But he acknowledged that Mr Foley had been warned in the past about a previous message.
Mr Hastert insisted he would not stand down and that he expected to win in the November 7 election and to run again as speaker.