Former US Congressman Mark Foley, who has been embroiled in a scandal over sexually suggestive e-mails, says he is undergoing treatment for alcoholism.
Foley checked himself into an undisclosed clinic at the weekend
The Florida Republican had checked himself into a rehabilitation facility, his lawyer said.
Mr Foley was forced to resign on Friday after it was revealed that he had sent sexual messages to young men, the youngest aged 16, on his staff.
Senior US politicians have called for a full inquiry into his conduct.
And the FBI is examining the messages to see if any law has been broken.
The message scandal has led to accusations that senior Republicans may have been aware of the communications but decided to ignore them.
"Republican leaders admitted to knowing about Mr Foley's abhorrent behaviour for six months to a year, and failed to protect the children in their trust," the Leader of the House Democrats, Nancy Pelosi, said.
House Speaker Dennis Hastert hit back at the charge.
"Anyone who had knowledge of these instant messages should have turned them over to authorities immediately, so that kids could be protected," he said.
"I repeat again: the Republican leaders of the House did not have them."
Mr Foley's lawyer, David Roth, refused to identify which rehabilitation unit his client was being treated in, although he did say that Mr Foley had gone in for treatment at the weekend.
"I strongly believe that I am an alcoholic and have accepted the need for immediate treatment for alcoholism and other behavioural problems," Mr Foley said in a statement quoted by the Associated Press news agency.
Mr Foley - a member of the House of Representatives caucus on missing and exploited children - apologised when announcing his resignation on Friday.
Mr Hastert on Sunday urged the justice department to investigate Mr Foley's messages to pages - students serving as messengers and assistants to members of Congress.
Some messages were sexually explicit and at least one of the recipients was only 16 years old.
The White House and Democratic leaders in Congress also called for a criminal inquiry.
"There is going to be, I'm sure, a criminal investigation into the particulars of this case," said White House counsel Dan Bartlett - who called the allegations "shocking".
The BBC's Justin Webb in Washington says that over the weekend it became clear that what started as a minor embarrassment for the Republican party had the potential to become something far worse.
It has emerged that Mr Foley's behaviour had been known about for some time by senior colleagues, including the party's leader in the House.
They are now arguing about how much they knew - but the Democrats and some Republicans have called for the party's Congressional leaders to step down.
Our correspondent says the scandal could cost the Republicans votes in next month's mid-term elections - votes they cannot afford to lose.