"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 spokesman was quoted as saying by The Telegraph.
The ministry reportedly buys fuel from a range of suppliers, including jet fuel from Greek company Motor Oil Hellas, which signed a five-year deal with Russia's Rosneft in November 2017.
Tanker tracking data shows that shipments of fuel oil have been sent from Russia to Motor Oil's terminal in Corinth since the start of the special operation in Ukraine. The spokesman said that the ministry was assured that the fuel obtained from Motor Oil Hellas was not sourced from Russia.
The UK announced in March it would phase out imports of Russian oil by the end of 2022, in response to the Russian security operation in Ukraine. Russian imports accounted for 8% of the country's total oil demand and 18% of diesel before the operation began.