Diesel prices have soared by an average of 18p per litre since the start of the Middle East conflict, new figures suggest.
The RAC said the average price of the fuel at UK forecourts on Sunday was 160.3p per litre.
This is compared with 142.4p when the US-Israeli campaign against Iran began on February 28.
The 13% increase means diesel is at its most expensive level since November 2023.
Petrol prices are up 7% over the same period, rising from 132.8p per litre to 141.5p per litre.
The last time petrol was more expensive was August 2024.
Oil prices – which have a significant effect on the cost of wholesale fuel – have exceeded 100 dollars a barrel for the first time since 2022 in response to Iran's stranglehold on oil tankers passing through the Strait of Hormuz.
RAC head of policy Simon Williams said: "Drivers with diesel cars are really feeling the heat.
"Prices have shot up 18p a litre in just two weeks, adding £10 to the cost of a full tank.
"The average cost of filling up a 55-litre family car with diesel is now £88, whereas for petrol it's £78.
"The UK has fewer refineries than ever and those we do have are more geared towards petrol production than diesel, so we're reliant on imports which has contributed to diesel prices rising faster."
Chancellor Rachel Reeves told petrol retailers last week they had a "shared obligation" to keep prices down for motorists.
The Petrol Retailers Association (PRA) had threatened to pull out of the Downing Street meeting with Ms Reeves and Energy Secretary Ed Miliband after claiming the Government's "inflammatory language" over rising fuel prices had led to abuse against forecourt workers.
At the Downing Street meeting, Mr Miliband warned executives from the forecourt operators and firms including Asda, BP, ExxonMobil and Shell that the Government would not tolerate "unfair practices" in the industry.
The Chancellor hosted industry chiefs in 11 Downing Street on March 13 in response to rising concern about the impact of the Middle East crisis on household finances.
