On Wednesday Lyudmila Navalnaya filed a lawsuit demanding it be released, amid suspicions her son was poisoned.
The Government called for a transparent investigation into Mr Navalny’s death and for his body to be released to his family.
The Prime Minister told the Commons: “The whole House will join me in sending our deepest condolences to the family of Alexei Navalny. He died for a cause to which he dedicated his whole life, freedom.
“Together with our allies we are considering all options to hold Russia and Putin to account and this morning we sanctioned those running the prison where Alexei Navalny’s body still lies.”
Mr Sunak paid tribute to Navalny, 47, who flew to Germany in 2020 for life-saving treatment after being poisoned by a Soviet-era nerve agent.
He returned to Russia in 2021 to continue his fight against Putin and was arrested.
“To return home knowing that Putin had already tried to have him killed was one of the most courageous acts of our time,” Mr Sunak said.
Transferred to Arctic Circle
In 2023, Mr Navalny was transferred to the “special regime” penal colony north of the Arctic Circle after being sentenced to 19 years on top of the almost 12 years he was already serving.
Lord Cameron is expected to confront his Russian counterpart Sergey Lavrov over Mr Navalny’s death at the G20 foreign ministers’ meeting in Rio on Wednesday and Thursday.
The two men won’t meet but the former prime minister is expected to use media appearances to attack the close Putin ally.
“No-one should doubt the oppressive nature of the Russian system,” Lord Cameron said on Wednesday.
At least 400 people mourning Mr Navalny have been detained in Russia since his death. On Wednesday, reports emerged of men paying tribute to the opposition leader being forced to report to the military.
Vladimir Putin has stolen “the future and democracy of the Russian people”, Sir Keir Starmer told MPs during Prime Minister’s Questions.
‘Consider sanctions against 8,000 people’
The Labour leader said: “I’m sure the whole House will join in sharing our disgust at the death of Alexei Navalny, who as the Prime Minister said died because of his efforts to expose the corruption of the Putin regime.”
Labour had called on Mr Sunak to consider sanctions against almost 8,000 people named on Mr Navalny’s list of Putin’s cronies.
The original list named 35 individuals linked to his poisoning and imprisoned but has been expanded to include 7,945 people including those accused of being oligarchs, human rights abusers and involved in corruption.
Only about 1,162 people identified by Mr Navalny’s Anti-Corruption Foundation have been sanctioned by Britain, the organisation said.
Only Canada sanctioned all 35 people included in the original list. The UK and Australia sanctioned 29 each. The EU took action against 26 and the US 24.
There was criticism that the asset freezes and travel bans did not go far enough to hurt Putin’s henchmen.
‘Similar weakness against Myanmar military’
Mark Farmaner, director at Burma Campaign UK, said Britain had imposed similarly weak sanctions on members of the Myanmar military.
“There are probably no assets to freeze,” he said on social media. “The default UK response to human rights violations is basically a ban on taking holidays in the UK.”
The EU approved a 13th package of sanctions against Russia on Wednesday. They target nearly 200 entities and individuals accused of helping Moscow procure weapons or of involvement in kidnapping Ukrainian children.
The sanctions come after Donald Trump yet again compared his legal troubles to the persecution of Mr Navalny while on the campaign trail ahead of this year’s US presidential elections.
“It is a form of Navalny. It is a form of communism or fascism,” he said of his recent $355 million fine for fraudulently inflating the value of his properties.
Mr Trump is seen as soft on Putin after praising the Russian leader when he was US President and there are fears over continued US aid to Ukraine if he is elected again.
‘Navalny’s death is being expolited’
Germany has demanded Russia explain Mr Navalny’s death. His widow Yulia gave an emotional speech to the Munich Security Conference last weekend, in which she vowed to continue her husband’s work.
Tino Chrupulla, one of the leaders of the hard-Right pro-Putin Alternative for Germany party, claimed the speech was “stage-managed” to benefit Ursula von der Leyen.
Mrs von der Leyen, a former German defence minister, had recently announced she would stand for a second term as European Commission President.
“It is obvious that Navalny’s death is being exploited,” Mr Chrupulla, a eurosceptic, said in Berlin.
‘No investigation yet’
The Bundestag member said it was “unbearable” that Putin was being blamed for Mr Navalny’s death.
“People are speaking about ‘murder’, and other things, even though nothing is known, even though there has not even been an investigation yet,” he said.
“Bluntly intervening in Russia’s internal affairs while paying lip service to the principle of sovereignty is trademark UK government hypocrisy,” the Russian embassy in London said after the sanctions were announced.
“In the meantime, Russian citizens are being killed with British ordnance and missiles supplied to the failing Kiev regime,” the embassy posted on X.
Russia has accused Ukraine of using UK-supplied Storm Shadow missiles to hit Russian-occupied Ukrainian cities.
