Just before xmas Snuggles joined our family. He was 12 weeks old and good as gold. The second we got him home he went in his litter tray and continued doing so whilst we lived there.
Three months ago we moved house. At first Snuggles would use the litter tray then we started letting him out when he was big enough. Since then he refuses to use the tray, preferring to use the floor!!!
Some mornings i'll wake up and he would have done his business in the tray but 9 times out of 10 he goes on the floor but kicks the litter out of the tray on top of the mess.
We keep the litter tray clean so we don't know what to do. The floor is getting ruined and the house stinks, then there is the added factor of this being unhygienic.
I had one cat that refused to use normal shop bought litter,we had to dig soil from the garden daily for him.He was quite happy with it and it made cleaning his tray a lot easier in the end because we could just empty it outside and it naturally degraded :)
Soil sounds a good idea. I would also move thelitterbox to a new place away from the smelly area.put some orange peel around the smelly area to keep the cat away from there.
You could start with soil.....then add a bit more litter to it with each change.....then he may get used to it again gradually. Would your paritner rather soil or pooh on the floor...?? Put some heavy plastic sheeting or a vinyl offcut under the tray..
What do you clean your litter tray with or the area close to it? I had this problem with my older fastidious cat a few years ago. Turned out my bf at the time was wiping the edge of the cat littler tray with lemon scented kitchen spray. Cats hate citrus.