A senior Iranian diplomat has hit back at the British prime minister for pressuring Tehran to “immediately” release a dual national, who has been held in Iran for four years, saying London’s efforts to blackmail Tehran by taking its own money hostage in exchange for inmates will fail.

Iran’s outgoing deputy foreign minister, Abbas Araqchi, made the remarks in a post on his official Twitter account on Saturday in response to a Friday tweet by UK Prime Minister Boris Johnson, who reiterated his “call for Iran to do the right thing” and immediately release Anoosheh Ashoori — a British-Iranian dual national on the fourth anniversary of his arrest in Tehran.

The prime minister claimed that Ashoori and other British nationals are unjustly imprisoned in Iran and must be able to return to their families in the UK.

Ashoori, who previously lived in south east London with his family, was detained in August 2017 and was sentenced to 10 years in prison for cooperating with Israel’s spy agency Mossad and two years for obtaining 33,000 euros in “illicit funds” nearly a year later.

In response to Johnson’s tweet, Araqchi said, “UK tries to blackmail Iran by taking our OWN money- illegally kept for more than 40 years- hostage in exchange for prisoners. This is never going to work.”