The British Ministry of Defense has threatened to abandon fuel suppliers that use Russian oil, a ministry spokesperson said on Sunday. 

"If oil products supplied to the Ministry of Defense are found to come from Russian suppliers, we will take immediate action to switch to alternate suppliers," The Telegraph quoted the spokesperson as saying.

London's defense ministry reportedly acquires its fuel from various suppliers, including jet fuel from the Greek Motor Oil Hellas, which had signed in November 2017 a five-year deal with the Russian Rosneft company.

Tanker tracking data shows that shipments of oil had been sent from Russia to Motor Oil's terminal in Corinth, Greece, since the start of the Ukraine war and the oil embargo on Moscow.

The spokesperson said that the ministry was assured that the fuel obtained from Motor Oil Hellas was not sourced from Russia, however.

The United Kingdom announced in March that it would stop importing oil from Russia by the end of 2022 in response to Moscow's actions in Ukraine. Russian imports accounted for 8% of the country's total oil demand and 18% of diesel before the war kicked off.

Western countries have imposed batches of sanctions on Russian oil, gas, currency, and more. The United States has banned Russian fuel imports, while the United Kingdom and the European Union have agreed to phase out their use.

Conversely, Asian countries such as China and India have increased their imports of Russian fuel, lured by record discounts of more than 30% on Brent crude.

Russia has been able to absorb the discounts caused by the rise in the price of Brent crude. Urals, Russia's main export blend, averaged $78.81 per barrel in May, up nearly 12% from the previous month.

The average price of diesel has reached a new high of 190.92 pence per liter, while gasoline has risen to 185.04 pence.

According to RAC calculations, a 55-liter family car with diesel now costs £105.01 ($128.14), while a full tank of gasoline costs £101.77 ($124.19).

"The speed and scale of the increase is staggering… Incredibly, the government is now raking around £46 ($56) in tax from every full tank," RAC fuel spokesman Simon Williams said in a statement cited by Bloomberg.

UK motoring groups have urged the government to take more decisive action to assist drivers in dealing with the price increase. The government already reduced fuel duty by 5 pence per liter in March, but motorists deemed the reduction insufficient. According to the RAC, a further reduction in fuel tax is long overdue but would still be "very welcome."