If your cat chooses to scratch your furniture over a scratch post, it may be that the scratch post isn't fit for purpose. Find out more about why your cat won't use a scratch post.
your cat is not being naughty, he is indulging in a natural behaviour and the fact that he is avoiding the provided facilities in favour of your furniture indicates that what you've given him isn't fulfilling its purpose.
It's important to realise that scratching (or 'stropping') not only keeps claws trim and encourages stretching, it also has a very important scent-marking function, plus it helps cats leave a visual sign of 'ownership' to others. The noise it makes is also a signal. Cats mark their territory in this way when they need to reassure themselves. This habit will therefore increase when a cat feels insecure, and when owners become 'aggressive' by scolding, clapping hands or using water pistols.
If you're already giving your cat lots of toys and attention it would be advisable to check that these are to his taste, and rotate them so he doesn't get bored. Attention also needs to be available entirely on the cat's terms, and not intrusive cuddling and so on. Concentrate on interactive play with fishing rod-style and thrown toys, which also increases physical exercise and can help decrease frustration.
Then look at your facilities. Lots of hiding places are essential, especially as stress could be a feature here. Often scratch posts are too unstable, too short and have material with a horizontal thread, not vertical, so they aren't used. Cats also need them where they feel most vulnerable. Doors to rooms and anywhere they feel intimidated, say open hallways where there is nowhere to hide, also need this sort of facility. We need to experiment to see what our pets want.
Look at where your cat scratches and work out the characteristics of the place. Then improve his scratching facilities. You could also wrap carpet pieces around stair posts or stick them against the wall, ensuring they are stable.
Remove the temptation to over-mark by smoothing the roughened bits, cover the areas temporarily to eliminate the visual cue drawing him to scratch again, and rub his own scent - picked up on a cloth by wiping his face - there to reassure him. Scratching can also be used by your cat to attract your attention so try to anticipate when he will do it and play or feed him to divert his attention before he starts.
Advice given by behaviourist Francesca Riccomini.