Heat the oil in a large skillet over medium heat. Add the onion, celery, bell pepper and garlic and cook until tender, about 5 minutes. Add the oregano, wine, diced tomatoes, tomato paste, sugar, bay leaf, salt and pepper. Bring to a simmer and cook 10 minutes. Add the seafood and cook just until the mussel and clams open and the prawns and cod is cooked through. Sprinkle with parsley and serve.