Boris Johnson demands 'immediate' release of Nazanin Zaghari-Ratcliffe in call with Iran's president

Boris Johnson has demanded the immediate release of Nazanin Zaghari-Ratcliffe, the British-Iranian mother detained in Iran on dubious spying charges, in a combative phone call with the regime's president.

"The Prime Minister raised the case of Nazanin Zaghari-Ratcliffe and other British-Iranian dual nationals detained in Iran and demanded their immediate release," Downing Street said in a statement on Wednesday, after Mr Johnson's call with Hassan Rouhani.

Ms Zaghari-Ratcliffe completed her five-year sentence on Sunday and had her electronic ankle tag removed, but Iran has refused to let her return to Britain.

Instead, officials have summoned her to a court hearing on Sunday, where it is feared she will face further charges.

"[Mr Johnson] said that while the removal of Nazanin Zaghari-Ratcliffe's ankle monitor was welcome, her continued confinement remains completely unacceptable and she must be allowed to return to her family in the UK," Downing Street added.

Ms Zaghari-Ratcliffe's husband, Richard Ratcliffe, has warned that she is being held hostage as part of an ongoing legal dispute with Britain over a tank debt from the Seventies.

Ms Zaghari-Ratcliffe was arrested in 2016 while visiting Iran and jailed over spying charges that have been widely disputed. Towards the end of her sentence, she was released from the notorious Evin prison and placed under house arrest with her family in Tehran.

Iran has linked her detainment to a Seventies-era tank deal that was only partially fulfilled by Britain, and which is now the subject of a legal tussle.

In 2008 an international arbitration court found that the UK owed the money, but Iran and Britain disagreed as to whether London should pay interest. The next court hearing in the case is due next month.

Mr Ratcliffe says that he and the relatives of other detained British-Iranian citizens are being used as leverage to recover the debt, and is frustrated that UK diplomats do not acknowledge this. Human rights groups have also called for Ms Zaghari-Ratcliffe's release and expressed grave concerns over the fairness of the Iranian judicial system.

Kate Allen, the director of Amnesty International UK, said: "Nazanin has already been convicted once after a deeply unfair trial before a Revolutionary Court, so of course we're extremely concerned about this hearing."

She added that Iranian authorities "systematically violate fair trial rights" and that it was of the "utmost importance" that UK officials were allowed to attend any court hearings.

Downing Street has previously said that officials have been denied access to legal proceedings because Iran does not recognise dual nationality.

In the statement, Downing Street said Mr Johnson had also put pressure on Iran to become a less "destabilising" presence in the Middle East. "The Prime Minister also stressed that while the UK remains committed to making the Iran nuclear deal a success, Iran must stop all its nuclear activity that breaches the terms of the [Joint Comprehensive Plan of Action] and come back into compliance," it said.

"He stressed the importance of Iran seizing the opportunity presented by the United States' willingness to return to the deal if Iran comes back into compliance."

A senior former diplomat said this week that Britain was exploring ways of paying off the debt without falling foul of US sanctions.

Lord McDonald, who was permanent undersecretary of the Foreign Commonwealth and Development Office until last September, told the BBC's Today programme: "We acknowledge it is Iranian money and it does have to go back to Tehran.

"A key complication is that Iran is subject to very comprehensive sanctions, so how this money is repaid is part of the story."