Off the top of my head, and I am entirely open to correction, AFAIK the answer is no, to the extent that PPR relief would render any gain on the same house exempt from CGT. The general rule is, if a gain on a disposal wouldn't be chargeable to CGT then a loss on the same disposal can't be allowable.
So if the house was PPR (i.e. the owner's family home) for the entire period of ownership, then there will be no allowable loss for set off - if it was only PPR for part of the period of ownership then there may be some allowable loss.
I may be way off the mark here - I'll check the legislation later if no-one else has given a definite answer...