According to the RAC, the average unleaded price will fall by 3p a litre in the next fortnight and diesel by 5p after oil prices fell below $40 a barrel for the first time since February 2009. This will take average prices to around 103p for petrol and 104p for diesel. Diesel is already at a six-year low, with the average price reaching 109.18p on Friday.

RAC Fuel Watch data shows oil prices have continued to fall since OPEC’s meeting in Vienna on Friday where delegates dismissed cutting production to stabilise the price. The end of day price for a barrel of Brent crude fell from $41.80 last Friday to $39.77 on Monday. Twelve months ago a barrel cost $65 and in June 2014 it was $115.

RAC Fuel Watch spokesman Simon Williams said: “With the price of wholesale unleaded dropping due to oil falling below $40 the climate is right for £1 a litre petrol, all we need is for the supermarkets to do the right thing and embrace the season of goodwill by passing on those savings at the pump to make Christmas that bit cheaper for everyone.

“Motorists have already enjoyed petrol at under £1 as one supermarket cut prices at its 277 nationwide forecourts as part of a three-day promotion at the end of November, but this should now become a common sight across the country. If retailers don’t pass on the savings quickly, they will be giving themselves an unpopular Christmas boost to profits by pocketing the extra margin when they should really be passing this on to their customers instead.

“The long-term outlook is for the oil price to stay low. OPEC is not due to meet again until June 2016 so unless an extraordinary meeting is called, it is anticipated production will continue to outpace demand and in turn keep wholesale fuel prices low.”