Motoring provides a very substantial part of the governments finance plans, and it represents a significant proportion of the revenue it collects.
There have been several studied that have come to the conclusion that the motorist accept that fuel prices will increase, and they will absorb modest increases and not radically change their driving habits. The governments 2p per litre tax increase schedule was based on this premise. However the rate of increase has recently been much greater than expected due to speculation of the fuel a and futures markets and motorists and hauliers are now seeing massive price jumps.
It is likely that the government will postpone its next proposed 2p increase, but due to the increased costs of the fuel, they are already collecting more from the VAT element of the fuel revenues, so they do not HAVE to ramp up the duty to meet their revenue plans.
Due to Govt' policy diesel was taxed more to give rise to about a 2p per litre differential over petrol. (purely a political decision) We are now seeing differentials of 5 to 8p on the same forecourt, This is in the hands of the oil companies and I cannot see any justification for this. However diesel engines are still substantially more fuel efficient than their petrol equivalents, and so it is still more economical to run a diesel on the basis of consumption.
Because of the UE laws, each member state has its own tax raising powers. It is not possible to make direct comparisons between fuel prices between member states. because of the different levies each state applies. You need to look at whole motoring costs and taxes not just fuel levies.