Republican Representative Trent Franks of Arizona says he is quitting amid a US House Ethics Committee investigation of possible sexual harassment.
Franks said in a statement that he never physically intimidated, coerced or attempted to have any sexual contact with any member of his congressional staff.
Instead, he said the dispute resulted from a discussion of surrogacy. Franks and his wife have three-year-old twins who were conceived through surrogacy.
Franks says he had become familiar with the surrogacy process in recent years, and "became insensitive as to how the discussion of such an intensely personal topic might affect others".
He said he regrets that his "discussion of this option and process in the workplace" with two female staffers made them feel uncomfortable.
He was speaking on Thursday after after the House Ethics Committee said it would investigate allegations of sexual harassment.
His resignation will take effect on January 31.