Bishop Nicolas Brouwet said the project was costly and too far from the grotto where the Virgin Mary appeared.
The current baths are drab and cold and pilgrims are rushed through, often after waiting in long queues.
The new baths, to be built on the meadow across the Gave River from the grotto, would have had individual changing cabins, spaces for prayer and a new options to just wash the face and hands rather than take a full-body dip in the chilly waters.