Around 50 Labour MPs have already signed a petition, calling on Darling to change his plans or risk severely damaging the Government.
Because the proposed increases will hit larger, older cars typically owned by less well-off families especially hard, the MPs fear that it will strike at the core of the Labour Party's traditional supporters.
That would compound the bad publicity and ill-feeling already generated by the recent 10p tax band debacle, which threatened to leave some of the UK's lowest earners worse off.
Labour MP Austin Mitchell is leading the MPs' opposition to the VED tax band changes. He says: 'It is a bombshell that will explode when it comes into force.'
It also comes at a time when petrol and diesel prices have hit record levels, putting the public's focus on the cost of motoring and the high taxes associated with it.