If the dog is always hungry, try the green bean diet. Reduce the dog food but give cooked green beans with it to compensate so that the dog feels full after the meal. Green beans are fine for dogs, are mostly water and fiber, and don't have many calories. Don't substitute starchy veggies (corn, carrots, rice, peas etc) because they do have lots of calories.
I put my dog (a coonhound) on a diet as he was almost 95 pounds and I understand that Bassets get fat, a common problem. For my Moses, I just reduced the food I gave him by almost 1/2 and now he is looking great - but you could try just giving your dog 1/2 cup less of food each day and after about 2 months your dog will probably be thinner.
Mercy
Do they get treats too? I would cut out treats and cut back even more on the food. When reading recommended amounts you can't go by weight if the dog is overweight. Ask you vet what should they weigh and then use that as the recommended feeding weight on the label. If what your feeding is still less than that try cutting back more or changing to another food. You can use carrots for treats or canned pumpkin. They are high in fiber and will help keep things moving :)