In a car showroom, it would probably be ‘slightly-used’ Labour, even adding that it has only had one previous careful driver. (Well, surely, there must be one of the previous drivers who could be described as careful?)
But perhaps a better answer might be ‘shop-soiled Labour’. It’s not old, but not quite new, and comes with only a limited guarantee as to its efficacy. I wonder if that’s what Hain meant.