Prime Minister Andy Burnham has said the UK will continue "to support Ukraine 100%", after Moscow warned of "consequences" following confirmation that British-made drones were used in recent Ukrainian strikes in Russia.
"We are not fair-weather friends, we will be there in Ukraine's hour of need and that won't change," said Burnham.
The Russian embassy to the UK earlier accused Britain of "deliberately opting for an escalation of the Ukraine crisis", adding that "the deeper its involvement in the conflict... the higher the price it will pay".
Ukraine has stepped up attacks on Moscow and elsewhere deep inside Russia, particularly targeting oil refineries and logistics sites for its key online retailer Wildberries.
Asked about the Russian threat, the prime minister maintained the UK was "providing support so that Ukraine can defend itself and that's been the British position all the way through this conflict, by previous prime ministers - it remains the case with me".
Russia has warned the UK in the past over its role in providing Ukraine with drone technology, as well as Storm Shadow missiles. The Russian embassy said "London's actions will inevitably carry consequences for which it will have to answer", but did not elaborate on the type of threat Moscow was considering.
The latest phase of the war has directly affected Russia's domestic fuel supplies and dented the Russian economy.
The UK has been among Ukraine's biggest international supporters since Russia launched its full-scale invasion in February 2022. The Ministry of Defence (MoD) said the UK was "committed to providing the equipment Ukraine needs to defend itself against [Russian President Vladimir] Putin's illegal invasion".
Russia currently controls approximately a fifth of Ukrainian territory but its forces have had very little success on the front line for months.
Nevertheless, casualties have continued to mount behind the front lines.
United Nations officials say last month's civilian death toll of 437 people in Ukraine was the highest since May 2022. In Russia, a foreign ministry spokesman told the Tass news agency on Tuesday that in the past week 69 people including three children had been killed.
In the latest Russian attacks on Ukraine, 17 people have been killed, including 10 in the village of Pechenihy in north-eastern Ukraine early on Tuesday.
Private homes, a cafe and post office were hit, as two missiles claimed the lives of 10 villagers. Elsewhere, three Ukrainians died in Sumy, two in Zaporizhzhia and two in Kherson.
Moscow's warning to the UK comes after a wave of Ukrainian strikes on Russia. Five people were killed in a residential area of Rostov region in the south of the country at the weekend.
Hundreds of drones have been launched by Ukrainian forces towards the Moscow region in the past two days alone. Regional governor Andrey Vorobyov said on Tuesday that a 10-year-old girl was hurt and a Wildberries warehouse was damaged.
As well as deploying imported drones, Ukraine has been able to use home-grown drone and missile technology in recent weeks, including its FP-5 Flamingo cruise missile.
Two British companies are known to have built drones supplied to Kyiv. A military source confirmed to the BBC that UK drones had been used in recent attacks on Russia, which are said to have caused more than £35bn in economic damage.
In April, the UK defence ministry announced it would supply Ukraine tens of thousands of drones, including long-range strike devices, in its biggest package of military aid so far.
Andy Burnham told Ukraine's President Volodymyr Zelensky when they visited a British naval base late last month that he "can count on the UK for as long as it takes". Burnham also said the UK would share its new "Stone Cloak" technology with Kyiv which would enable electronic jamming of Russian air defences.
Russia has long complained of the use of UK drone technology in the war. In 2024, foreign ministry spokeswoman Maria Zakharova said drones using UK components and configurations were used to attack Russian territory, including a fuel depot in the Kamensky district of the Rostov region.
