With a pivotal government witness waiting in the wings, a defense lawyer in the Enron fraud trial sought Monday to cast doubt on a former executive’s dramatic claim that CEO Jeffrey Skilling fretted in 2001 that “they’re on to us.”

Kevin Hannon, a former Enron Corp. broadband unit executive, testified last week that Skilling made the remark when analysts criticized sales Enron made to partnerships run by its own chief financial officer, Andrew Fastow.