Coat a Dutch oven with cooking spray, and add margarine. Place over medium-high heat until margarine melts. Add onion, celery, and garlic; saute until tender.
Drain clams, reserving liquid; set clams aside. Add reserved clam liquid, potato, and bottled clam juice to onion mixture; stir well. Bring to a boil; cover, reduce heat, and simmer 20 minutes or until potato is tender. Let cool slightly.
Position knife blade in food processor bowl; add potato mixture. Process 1 to 2 minutes or until smooth; return mixture to pan.
Place flour in a medium bowl; gradually add milk, stirring with a wire whisk. Add flour mixture to potato mixture; stir well. Stir in reserved clams, Canadian bacon, thyme, pepper, and hot sauce. Cook over medium heat 20 minutes or until thickened and bubbly, stirring frequently. Ladle into individual bowls, and sprinkle with chopped parsley.