The Prime Minister of the United Kingdom, Keir Starmer has said Russian oligarch Roman Abramovich must "pay up now" to victims of the war in Ukraine or face court action.

Mr Abramovich, the former owner of Chelsea Football Club, pledged in 2022 that the £2.5bn he made from the sale of the club would be used to benefit victims of the Russian invasion of Ukraine.

But there has been a delay in releasing the funds, which are currently frozen in a British bank account, due to a standoff over how exactly they should be used.

The government wants the money to be used for humanitarian aid, but Mr Abramovich insisted it should be used for "all victims of the war" – meaning that Russians could also benefit.

The oligarch cannot access the money under UK sanctions but the proceeds from the Chelsea sale still legally belong to him.

"If Mr Abramovich fails to act quickly, this government is fully committed and prepared to going to court to enforce that commitment if necessary," a government spokesperson said.

They said the funds "would strengthen frontline capacity, enhance protection for the most vulnerable and support sustainable solutions that help Ukraine move from crisis response to long-term resilience".

"It would be hard to overstate the impact that an additional two and a half billion pounds could have for the people of Ukraine."

Mr Abramovich's representatives declined to comment.

Speaking in the Commons, Sir Keir Starmer said the UK had issued a licence "to transfer £2.5bn from the sale of Chelsea Football Club that's been frozen since 2022."

Sir Keir said: "My message to Abramovich is clear: the clock is ticking.

"Honour the commitment that you made and pay up now, and if you don't we're prepared to go to court and ensure that every penny reaches those whose lives have been torn apart by Putin's illegal war."

The Treasury said that under the terms of the licence, the money must go to "humanitarian causes" in Ukraine and cannot benefit Mr Abramovich or any other sanctioned individual.

The government first threatened to sue Mr Abramovich in June.

Chancellor Rachel Reeves said: "It is unacceptable that more than £2.5bn of money owed to the Ukrainian people can be allowed to remain frozen in a UK bank account."

Mr Abramovich – a Russian billionaire who made his fortune in oil and gas – was granted a special licence to sell Chelsea following Russia's invasion of Ukraine, providing he could prove he would not benefit from the sale.

He is alleged to have strong ties to Russian President Vladimir Putin, something he has denied.

It is understood that Mr Abramovich has 90 days to act before the UK considers taking legal action.

On Thursday, EU leaders are set to review proposals to use proceeds from frozen Russian assets to support Ukraine's huge budget and defence needs. Russia has fiercely opposed the proposals.