Speaking to members of parliament on Wednesday, Starmer said: “The clock is ticking on Roman Abramovich to honour the commitment he made when Chelsea FC was sold and transfer the £2.5 billion to a humanitarian cause for Ukraine.
"This government is prepared to enforce it through the courts so that every penny reaches those whose lives have been torn apart by Putin's illegal war."
Chancellor Rachel Reeves added: "It's unacceptable that more than £2.5 billion of money owed to the Ukrainian people can be allowed to remain frozen in a UK bank account. It's time for Roman Abramovich to pay up.
"If he doesn't act then we are prepared to do what is necessary to make sure that money gets to the Ukrainian people."
Foreign secretary Yvette Cooper also said: "This money was promised to Ukraine over three years ago. It is time Roman Abramovich does the right thing, but if he won’t we will act.
"That’s why the licence has been issued. It is time this money was used to rebuild the lives of people who’ve seen devastation as a result of Putin’s illegal war."