The Islamic regime went ahead with the killing just hours after British Foreign Secretary James Cleverly warned them not to execute Akbari, a former Iranian deputy defence minister.
Britain had described the death sentence as politically motivated and called for his immediate release.
Prime minister Rishi Sunak has said the execution of British-Iranian dual national Alireza Akbari in Iran was a ‘callous and cowardly act, carried out by a barbaric regime’.
Sunak, writing on Twitter after Iranian state media announced Tehran had executed Akbari on charges of spying for Britain, said: ‘I am appalled by the execution of British-Iranian citizen Alireza Akbari in Iran.
‘This was a callous and cowardly act, carried out by a barbaric regime with no respect for the human rights of their own people. My thoughts are with Alireza’s friends and family.’
‘Alireza Akbari, who was sentenced to death on charges of corruption on earth and extensive action against the country´s internal and external security through espionage for the British government’s intelligence service … was executed,’ Mizan said in a tweet.
It accused him of receiving 1,805,000 euros, 265,000 pounds, and $50,000 for spying.
In an audio recording broadcast by BBC Persian on Wednesday, Akbari said he had confessed to crimes he had not committed after extensive torture.
Iranian state media broadcast a video on Thursday January 12, they said showed that Akbari played a role in the 2020 assassination of Iran’s top nuclear scientist, Mohsen Fakhrizadeh, killed in a 2020 attack outside Tehran which authorities blamed at the time on Israel.
In the video, Akbari did not confess to involvement in the assassination but said a British agent had asked for information about Fakhrizadeh.
Earlier this week, Mr Akbari’s wife Maryam said an official asked her to visit her husband in prison for a ‘final meeting’ before the state killing.
He was transferred to solitary confinement, a sign that the execution was imminent after the death was sentenced and issued by the Revolutionary Court.
An audio message received by BBC Persia from Mr Akbari prior to his death claims he has been tortured and forced to confess on camera to crimes he did not commit.
He says he was forced to take psychedelic drugs and was interrogated for ten months.
‘With more than 3,500 hours of torture, psychedelic drugs, and physiological and psychological pressure methods, they took away my will.
‘They drove me to the brink of madness… and forced me to make false confessions by force of arms and death threats,’ he said.
Iran’s Ministry of Intelligence described the politician as ‘one of the most important agents of the British spy service’.
He previously worked in Iran’s military and security institutions and has joint citizenship of Iran and Britain.
He then served as the international deputy of the Ministry of Defence under two-star general Ali Shamkhani, who served from 1997 to 2005.