There is currently no poison that is approved to kill foxes. Use of such a product for this purpose may lead to prosecution resulting in a fine or imprisonment. Again the use of any gas to harm a fox is illegal and at present there is no product available approved for the gassing of foxes. It has been scientifically proven that it is the size of territory and availability of food that regulates fox numbers. Some actions intended to control foxes actually encourage them to breed more.
Deterrence is the most effective way of dealing with a fox nuisance.
It attempts to prevent foxes coming onto land in a humane way. The majority of complaints regarding the urban fox is the damage they cause to gardens and the killing of domestic animals and pets, for example rabbits and guinea pigs. Both these problems are easily solved without the painful death of the fox. Foxes digging up gardens or fouling can be deterred using an approved chemical deterrent. The pens, cages and runs that house animals outside can be made fox proof.