The Times of the 1800/01 period had a lot about the problems of French prisoners of war.
It seems that it had been the normal practice that the nation the troops belonged to supplied them with food and clothing even when they were prisoners ( I have no idea how this was arranged) but that Bonaparte, as First Consul had unilaterally decided that they shoudl be supplied by their captors. Since the British government hadn't been consulted they took offence and though they supplied food they refused to supply clothing and blamed the subsequent poor condition of the French prisoners on the French government. After a lot of reciprocal name-calling the British government gave in, being under some pressure from Parliament.
It was also said that the rations were adequate but that the French tended to gamble with them which cause dmuch of the distress.
I can't give more details, I only picked this up while was browsing the site recently.