May’s fuel price analysis figures have shown that diesel fell by a record of nearly 12p per litre.
The RAC said the average price of diesel at UK forecourts dropped from 158.9p to 147.0p in May.
But despite the reduction being the biggest monthly reduction since the company began tracking prices in 2000, it believes the cut should’ve been greater to fully reflect reductions in the wholesale market.
The price drop has lowered the cost of filling a typical 55-litre family car by around £6.50.
Petrol prices also dropped for the seventh consecutive month, with average costs reducing by 3p from 146.5p to 143.3p.
RAC fuel spokesman Simon Williams said: 'A 12p reduction in the price of diesel in one month is something we haven't seen in nearly 23 years of monitoring prices.
But with prices in Scotland still almost 7p higher than in Northern Ireland, both the RAC and AA have criticised Scottish leadership.
Mr Williams added: 'We're sure retailers in Northern Ireland are still making money – they've just done the right thing for their customers by moving prices down as wholesale costs have fallen.’
AA fuel price spokesman, Luke Bosdet, added: 'There is nothing stopping Scotland replicating the NI Fuel Price Checker. I suspect, though, that the government in Scotland is more interested in trying to relieve drivers of their cash, through workplace parking levies and city penalty charges, than helping them in a cost of living crisis.'
A Scottish Government spokesman said: 'Tools to help consumers find the cheapest fuel prices are readily available online. We expect petrol stations to charge all consumers a fair price and advertise these in a transparent and easily understood way.
'The Scottish Government has raised inconsistent pricing between urban and rural areas with the CMA as a key issue for the investigation they are conducting.'
