WASHINGTON — Representative Trent Franks of Arizona, one of the House’s most ardent social conservatives, said Thursday night that he would resign after the House Ethics Committee began an investigation into complaints that he had asked two female staff members to be a surrogate to bear his child.

In a statement, Mr. Franks said the discussion about surrogacy came up with “two previous female subordinates” because he and his wife, who have struggled with fertility, wanted to have a child. He said he regretted that the conversations had “caused distress.”

“Due to my familiarity and experience with the process of surrogacy, I clearly became insensitive as to how the discussion of such an intensely personal topic might affect others,” Mr. Franks said.

Mr. Franks denied that he had ever “physically intimidated, coerced, or had, or attempted to have, any sexual contact with any member of my congressional staff.”