One way or another, the Government needs to raise more money to be able to pay for its future spending plans.
Although the pro-motoring lobby suggests that there are ways of doing this without penalising motorists, the fact remains that as global pressure increases to reduce emissions, car owners are an obvious target.
Alternative suggestions include targeting people who use their cars the most, so that those who drive the farthest pay for their additional emissions.
Raising duty on fuel is the simplest way of doing this, because drivers would pay for driving thirsty cars and for driving longer distances.
However, with fuel prices at a record high and the public conscience focused on the fact that the UK's fuel taxes are already among the highest in Europe, this would undoubtedly be followed by swathes of criticism.
Road pricing is another possible, if controversial, solution.
Charging people to use main roads, as well as for driving long distances, would target motorists who travelled the furthest and most frequently, but would penalise business drivers and raise issues over the 'Big Brother' technology required to administer the scheme.
Alternatively, a new car tax on the highest-polluting vehicles has been suggested.
As the vast majority of the very highest-polluting vehicles are luxury cars such as Bentleys, Ferraris and Porsches, the suggestion is that they should have a tax added to their purchase price, making buyers pay up front for the pollution they will cause.