Petrol and diesel prices rose by around 3p a litre in December, taking the fuels to their priciest levels since July 2015.
An oil price rally triggered by a production cut among members of the Organisation of the Petroleum Exporting Countries (Opec) at the end of November pushed up the wholesale costs for both fuels by nearly 4p a litre.
Since 29 November, the last day before the major Opec agreement was announced, prices have risen around 20 per cent. A second deal with 11 non-Opec producers was agreed in December, boosting oil prices further.
RAC Fuel Watch data shows unleaded petrol climbed to 117.23p a litre on 29 December, up from 114.24p at the beginning of the month, while diesel prices reached 119.63p, up from 116.56p.
It now costs £8 more for a tank of petrol than it did at the same time last year and £10 more for diesel based on the end of January low price of 101.05p a litre.
"The rising oil price is bad news for motorists as it caused a nasty jump in pump prices in the most expensive month of the year," said RAC fuel spokesman Simon Williams.
"While forecourt prices rose by 3p a litre in December as the RAC predicted, they didn’t rocket as others had forecast. The big question now is how much further are they likely to go up, particularly in the long January wait to the next payday.
So far the price rises we’ve seen are purely down to the announcement at the end of November that Opec and non-Opec countries would be cutting oil production this month. Everything now depends on the strength of the deal and each country sticking to the agreed production levels. Russia will be of particular interest as it is currently producing at near record levels.