In a poll released on Sunday, the King’s birthday, almost two-thirds of Spaniards said they want their king to abdicate and hand the crown to his son, Prince Felipe.
King Juan Carlos, who has been on the throne for 38 years, was once one of the world's best-loved sovereigns, respected for his common touch and for helping guide Spain to democracy in the 1970s after the death of Francisco Franco.
The scandal of his daughter, Princess Cristina, and her husband, Iñaki Urdangarin - particularly at a time of economic crisis and widespread unemployment has not helped. Urdangarin has been charged with embezzling €6m in public funds. The couple deny any wrongdoing.
This follows the scandal in April 2012 when Juan Carlos fell and broke his hip during an elephant-hunting safari in Botswana, a lavish, privately funded trip that was secret until his accident.