How can I convince my father to bathe more often?

My father is 96 years old and mentally pretty sound, except that he will only bathe once a week. He has incontinence and bowel issues. He only changes his clothes once a week when he bathes, including underwear. He stinks so badly you can't be near him. I have asked, pleaded and demanded to no avail. I have tried to approach the subject of disposible protection. He gets upset and tells me to mind my own business. What can I do?