The Council will start the legal procedure only if the owner of the private land requests the Council to do so in writing. The Council generally deals with abandoned vehicles on the public highway, for example in streets within the District.
An untaxed vehicle?
You should contact the DVLA. The Council has no powers to deal with untaxed vehicles which have not been abandoned.
Found a vehicle parked illegally or dangerously?
Irrespective of whether a vehicle is taxed or not, these vehicles must be reported to the police as they can arrange for vehicles to be removed straight away.