FairFuelUK has the backing of a cross-party group of 32 MPs for its bid to eliminate what it describes as "opportunistic and unfair profiteering".
In particular, it says, the wholesale price of diesel is currently 6p less than petrol, yet retailers continue to charge more for it at the pumps – and the UK is only country in the EU where this is happening.
Howard Cox, founder of FairFuelUK, says: "RAC Foundation's latest figures clearly show that diesel drivers have been ripped off by more than £0.25 billion in the last six weeks at the pumps. This is brazen and unscrupulous profiteering by retailers exploiting 12 million motorists, white van drivers and the haulage industry."
He adds: "FairFuelUK calls on Brian Madderson, head of the Petrol Retailers Association, to come clean as to why such opaque and maverick pricing practices among his members continue unchecked for all vehicle fuels."