I recon you are right, it is in very bad shape, looks rather dangerous and to be honest if the image represents the quality of the timber I should possibly be condemned. What is the substructure like? If the structure is that bed then it should possible be replaced.
Maybe best to get something in writing and I would recommend taking plenty of images to safeguard you against any comeback.
Jeremy Bevan said:
Unfortunately the client just wants us to make good for the time being, otherwise I alsways recommend Ipe for new decks. Prob go for a softwood then althoug it willstick out like a sore thumb, prob best to Netrol clean the whole deck then to stain/oil the whole thing. Do you agree?