The average price of diesel at UK filling stations went up by 8.33p per litre in September, according to the RAC.
The motoring organisation said the rise, to an average of 163.11p per litre, came on the back of an 8p rise in August.
Petrol meanwhile has risen by 11p per litre over the past two months, to 157.01p.
The RAC said the price rises were being driven by oil producer group OPEC+ restricting global supply, in conjunction with the weaker value of sterling making wholesale fuel, which is traded in dollars, more expensive to buy in the UK.