"Your actions have amounted to a self-inflicted wound that has forced unnecessary suffering on the people of South Carolina," House Speaker Bobby Harrell said in a letter to the governor.
Mr. Sanford, appearing on an evening talk radio show in Columbia, said he planned to stay in office. He called his critics politically motivated and more interested in selling newspapers than portraying his tenure accurately.
"I'm not looking for a fight," he said. "I'm looking for the truth."
The call for Mr. Sanford to quit from Mr. Harrell, a Charleston Republican, is the first from one of the Legislature's top officers. It comes almost two weeks after a similar call from the lieutenant governor and after GOP House members threatened impeachment but took no other action.
Mr. Harrell would largely decide how any effort to force Mr. Sanford from office plays out. House Judiciary Committee Chairman Jim Harrison, R-Columbia, said he expects that a letter from the GOP caucus later this week will call for Mr. Sanford's resignation.
Three Associated Press investigations that raised questions about Mr. Sanford's travel have led one state senator to accuse the governor of breaking the law and also led to an ongoing state Ethics Commission investigation.
The AP investigations have shown that Mr. Sanford appears to have violated state law requiring lowest-cost travel when taking commercial flights; that he used state aircraft for personal and political trips, which is contrary to state law; and that he didn't disclose flights on private planes.
Mr. Sanford answered questions Tuesday from a handful of mostly affable callers on Columbia radio station WVOC-AM. He restated his argument that he has saved the state money on travel, has used state planes less than his predecessors and is being treated differently than other governors and state officials when it comes to commercial travel.