Petition Stop car insurance postcode lottery

When booking car insurance, the premium can increase by up to 400% just for a change in the postcode of the policy holder even for third party insurance which is independent of the home of the policy holder. I believe this is plain discrimination against people leaving in certain post codes. For instance, if a person moves from post code A to B, the insurance cost can increase from £1000 to £5000 even for a car worth less than £1000. This cannot be right as it is still the same person with the same driving skills and habits. The insurance should be based on the risks posed by the policy holder to other road users and a small increase in premium (proportional to the cost of the car) if the policy include fire and theft or is comprehensive.