I'd be inclined to argue that under trading standards legislation it is not fit for its intended purpose if used as a rabbit hutch. I would cite the RWA and RSPCA standards (RSPCA I think say 3-4 hops and able to stand up and stretch) and say that even the smallest rabbit wouldn't be able to do that. Maybe also see if you can find an RSPCA prosecution where rabbits were kept in hutches of a similar size - that way you can prove that a court of law has deemed it inappropriate.