CLARENCE, N.Y. – Rep. Christopher Lee of western New York abruptly resigned with only a vague explanation of regret after a gossip website reported that the married congressman had sent a shirtless photo of himself flexing his muscles to a woman whose Craigslist ad he answered.

“I regret the harm that my actions have caused my family, my staff and my constituents,” Lee posted in a surprise announcement Wednesday night on his congressional website. “I deeply and sincerely apologize to them all. I have made profound mistakes and I promise to work as hard as I can to seek their forgiveness.”

A woman described as a 34-year-old Maryland resident and government employee provided the Gawker website with e-mails she said were an exchange between her and Lee in response to an ad she placed last month in the “Women Seeking Men” section of Craigslist.

Gawker reported Wednesday that Lee, 46, identified himself as a divorced 39-year-old lobbyist and sent a photo of himself posing in front of a mirror.

In one e-mail, Gawker said, Lee described himself as “a very fit fun classy guy” and promised “not to disappoint.” He and the woman exchanged a few more messages, talking about recent dates and sharing biographical details.

In one, the site shows, the woman asks Lee if he’s divorced.

Yes, he replied, one minute later.

The woman told Gawker she eventually broke off the contact with Lee after becoming suspicious that he had misrepresented himself.

Lee, a two-term Republican with a young son, said in an e-mailed statement that his resignation was effective immediately. The statement offered no confirmation or details of a Craigslist post.

On Thursday, House Speaker John Boehner said Lee’s rapid resignation was his decision alone. “I think he made the right decision for himself and for his family,” the Ohio Republican told reporters in Washington.

Boehner said he became aware of the picture the previous afternoon and of the resignation just after 6 p.m.

Lee, who won his seat in 2008, cultivated a family-values voting record in the House, earning an 88 percent approval rating from the American Conservative Union for his 2010 votes. He voted in favor of a ban on federal funding of abortion in the health care overhaul, in line with the group’s position on the proposed ban, which was defeated in the House. He also voted against the repeal of the military’s policy prohibiting service by openly gay men and women.