Petition Stop changes to zero tax and congestion charge exemption limits.

Read in autoexpress that the Greener Vehicle Discount currently applicable to cars emitting 100g/km CO2 or less may be reduced soon to a lower limit of 80g/km CO2.
This change, whilst it might make cars greener still etc etc etc, would be unfair to those people who have purchased greener vehicles, that tend to cost more than their 'standard' equivalents. Moving the threshold like this would be cynical and represent a further reduction in motorists' trust in the people whom write the law.
Any changes to this would have to include a substantial 'grace' period of a minimum of 3-5 years.
I would ask the government to shelve any such proposals.