I had the problem once. I noticed that the local cats picked out my recently dug seed-bed for their deposits, so I dug an area away from the veg - this in a large shared garden which no-one else was gardening, and out of the way, and then put cut nettles over the veggies. These were a particularly ferocious type which had flourished where a neighbour had fertilised their patch with the treated sludge from the local sewage works. I expected to have to keep replacing the nettles with fresh, but the cats changed their habits fairly quickly, and I only needed to do it once.

Penny