If the towbar is after market fitted. It's always better to find where the wires are connected to the main loom rather than cutting them (could cause short to earth etc). The towbar loom is normally connected around one of the rear light clusters with crappy scotchblock, easily accessible from the boot. Open the blocks and remove along with the tow bar wire. Remember to replace the entry hole for the towbar wire with a rubber blank to stop water getting in.