This would take prices at the pumps falling to their lowest level since the end of May 2009, the RAC added.
It said that the price of Brent crude, now down below the $60-a-barrel mark for the first time since early July 2009, was predicted to keep on dropping.
The RAC added that it was hopeful that petrol would be sold nationally for under £1 a litre in the first few months of the new year.
RAC fuel spokesman Simon Williams said: “What’s currently happening at the pumps with falling fuel prices is something many motorists will not remember seeing before.
“Talk of prices going up like a rocket and falling like a feather could not be further from the truth as retailers have been quick to pass on savings at the forecourt since we forecast on December 6 that prices were due to come down by 7p a litre for petrol and 6p for diesel.”
As the cost of crude falls, Asda has sparked another likely round of supermarket fuel cuts by reducing the price of its petrol and diesel for customers.
It is cutting its petrol by 2p a litre and its diesel by 1p a litre, with the reductions taking effect from Friday.
The cuts mean Asda customers will pay no more than 110.7p a litre for petrol, with the company’s diesel costing 117.7p a litre.
Asda’s petrol trading director Andy Peake said: “We’re giving drivers an early Christmas present as fuel prices continue to fall. Asda are leading the way with our 11th price cut since September.”
Mr Williams added: “The cost of going to visit family and friends this Christmas will be the cheapest it’s been for nearly five years, but the prospect of petrol going below £1 a litre in the new year is incredible, particularly when prices at the beginning of 2014 seemed to be heading ever upwards.
“Current forecasts are for average petrol prices to fall to below 110p a litre in the next fortnight and diesel to drop to under 116p.
“At these average prices across the country the cheapest retailers will almost certainly be selling petrol for around 105p a litre, or even lower.”