The UK has delayed some sanctions on Russian oil and liquefied natural gas to help tackle soaring prices as the conflict in the Middle East disrupts global supplies.

A trade licence that came into effect on Wednesday permits the import of jet fuel and diesel refined from Russian crude in third countries while another lifts restrictions on shipping LNG from two Russian terminals.

Keir Starmer denied that the decision to postpone the restrictions – originally announced in October last year – would reduce pressure on Moscow, and promised to keep working with allies on further sanctions.

The prime minister told the House of Commons the “short-term” measures would help protect consumers from the impact of the crisis and were part of a “phase-in” of tougher new penalties targeting the Kremlin.

“This is not a question of lifting existing sanctions in any way whatsoever, and we will continue to work with our allies on further sanction packages,” he told parliament.

Chris Bryant, the business minister, told MPs the coming sanctions would be important in “ratcheting up the pressure on the Russian regime” but the government was implementing them “in a phased way” owing to the energy market instability caused by the Middle East conflict.

The UK decision was in line with the approach taken by Canada and Australia, and would be reviewed by the government “as soon as possible”, Bryant added.

The UK has for years led international efforts to put economic pressure on Moscow over its war on Ukraine. On Tuesday it signed a G7 statement reaffirming its “unwavering commitment” to imposing “severe costs” on Russia. It had previously announced it would block Russian oil refined in other countries to “further restrict the flow of funds to the Kremlin”.

Opposition politicians condemned the decision to postpone the sanctions. The Conservative leader, Kemi Badenoch, posted on X: “After 18 months of ‘standing up to Putin’ the Labour govt quietly issued a licence allowing imports of Russian oil refined in third countries.

“Yesterday Labour MPs voted against UK oil and gas licences. We are now importing from Russia instead of drilling in the North Sea. Insane.”

The decision follows similar moves from the US as Iran’s blockade on the strait of Hormuz continues to disrupt global energy provision, deepening concerns that the world may soon run out of spare energy supplies.

This week the US Treasury secretary, Scott Bessent, extended a 30-day sanctions waiver allowing the purchase of Russian oil shipments already at sea, saying in a post on X that the extension would “provide additional flexibility, and we will work with these nations to provide specific licences as needed”.

On Tuesday the RAC said the average price of a litre of petrol at UK forecourts stood at 158.5p, the most expensive it had been since December 2022. Several major airlines have been forced to cancel flights and increase prices because of the surging price of jet fuel since the war began in the Middle East, which typically supplied about a third of Europe’s jet fuel before the crisis.

On Wednesday, Starmer confirmed a widely expected extension to the temporary 5p cut in fuel duty. Announcing the freeze to the end of the year and a vehicle tax break for the haulage industry, the prime minister told the Commons they were a necessary response to cost of living pressures.

Relaxing sanctions will allow imports of jet fuel from India, previously a significant supplier to the UK and Europe. Russian crude is also refined in big quantities in Turkey.

Emily Thornberry, the chair of the foreign affairs committee, said it was the wrong time to relax sanctions. She told BBC Radio 4’s Today programme: “I’ve heard from people in Ukraine overnight and I know that they are very disappointed and have been asking me why it is that Britain is doing this.”

Thornberry said every time Vladimir Putin came to the negotiating table “he just takes the mickey”.

“He needs to really feel the impact of continuing to be involved in the war in Ukraine and we should not take a foot off the pressure now,” she said.