The UK government has loosened strict sanctions on Russian oil refined into diesel and jet fuel in third countries as prices rise.
The waiver begins on Wednesday and reflects growing supply concerns over certain fuels due to the effective blockade of the key Strait of Hormuz waterway since the start of the US-Israel war with Iran.
Some sanctions on the transport of Russian liquefied natural gas (LNG) were also lifted.
The government said that overall sanctions had got tougher but extra flexibilities were required. A similar move by the US was widely criticised.
European jet fuel prices more than doubled after the war started but are now around half higher while UK pump prices continue to rise.
According to motoring firm the RAC, the average price of unleaded petrol reached 158.52p a litre on Monday, the highest since the start of the war.
Several airlines operating in the UK and around the world have cancelled flights and raised prices in response to sky-high jet fuel prices.
For years the UK led international efforts to put economic pressure on Russia for its war on Ukraine.
Only on Tuesday it signed a G7 statement reaffirming its "unwavering commitment" to impose "severe costs" on Russia.
The government announced in October that it planned to ban oil products, such as diesel and jet fuel, which had been refined from Russian crude oil in third countries.
Easing sanctions now will effectively allow imports of jet fuel from India, which was previously a key supplier to UK and Europe. A lot of Russian crude is also refined in Turkey.
The new rules for sanctioned processed oil products will be of "indefinite duration", though they will be reviewed periodically and may be amended or revoked, the government said.
The UK also issued a time-limited licence covering the maritime transportation of LNG and related services under Russia sanctions rules, running until 1 January.
Treasury minister Dan Tomlinson told BBC Breakfast the "small and specific" and "time-limited" change was being made to "protect the security of supply for really important foundational goods in our economy such as jet fuel".
While the government remained "steadfast in its commitment to supporting Ukraine", he said, it had to "make the right and sensible decisions" when it came to vital products so that it could support families up and down the country struggling with the cost of living.
However, Robin Mills, chief executive of Dubai-based energy consultancy Qamar Energy, told BBC Radio 4's Today programme it was not a good move to back down on the sanctions and that it would not bring down prices in the UK.
"It is sending a negative signal that sanctions on Russia are potentially weaker because of the crisis in the gulf and that countries including the UK and the US will back down on sanctions because of other issues," he said.
He added he doubted that "there was ever a real prospect of physical shortages" of jet fuel.
"In that sense this measure looks unnecessary, its not going to bring down prices but its also not going to attack the shortage that probably wasn't going to happen anyway," he said.
The Labour chair of the foreign affairs select committee, Dame Emily Thornberry, said she opposed the government's decision to loosen some sanctions on Russian oil.
She told Today she had heard from people in Ukraine overnight and they were "very disappointed".
"We're talking about our allies in Ukraine who have been fighting a war bravely against Russia for years and years, with our support, and they have looked to Britain as one of their most important allies, and they don't understand," she said.
Responding to the point that the UK is following similar measures pursued by Spain and the US, Dame Emily added: "Just because other countries are behaving in the wrong way, does not mean we should join them."
Conservative leader Kemi Badenoch also criticised the move, saying that "after 18 months of 'standing up to Putin'", the government had "quietly issued a licence allowing imports of Russian oil refined in third countries".
She pointed out that on Tuesday Labour MPs had voted against issuing new UK oil and gas licences, but now the country was "importing from Russia instead of drilling in the North Sea".
Earlier this week, the US extended a similar waiver, first introduced in March, which loosened sanctions preventing other countries buying Russian oil and petroleum already loaded on vessels at sea.
US Treasury Secretary Scott Bessent said in March the "short-term measure" was aimed at promoting "stability in global energy markets".
The policy has been criticised by many US and UK allies who say it helps the government of Russian President Vladimir Putin and his full-scale invasion of Ukraine, which has been ongoing since 2022.
French President Emmanuel Macron has said that the Strait of Hormuz's shutdown "in no way" justified lifting the sanctions on Russia while Ukraine's President Volodymyr Zelensky has said "every dollar paid for Russian oil is money for the war".
However, UK Foreign Secretary Yvette Cooper refrained from criticising the US decision in March, describing it as a "specific, targeted issue".
A UK government spokesperson said it had "introduced a new wave of tighter restrictions on Russia including further export and import bans against Russia".
These included "restrictions on the sale of refined oil products derived from Russian crude oil and the import, supply and delivery to third countries of Russian uranium".
"The sanctions also include a new maritime services ban on Russian LNG which will progressively restrict Russia's access to the UK's world-leading shipping and insurance services, disrupting their ability to transport Russian LNG.
"Our support for Ukraine is unwavering - these additional sanctions will further restrict Russian revenues and degrade its ability to wage Putin's illegal war in Ukraine."
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