Boris Johnson has told Iran’s president, Hassan Rouhani, in a phone call that the British-Iranian aid worker Nazanin Zaghari-Ratcliffe must be allowed to return home to be with her family. “The prime minister raised the case of Nazanin Zaghari-Ratcliffe and other British-Iranian dual nationals detained in Iran and demanded their immediate release,” a statement from Johnson’s office said on Wednesday. “He 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.” Rouhani complained to Johnson that no practical progress had been made in solving Iran’s demand for the UK to return a £400m debt, adding: “Undoubtedly, accelerating the repayment of Iran’s claims would be effective in solving other problems in the UK-Iranian bilateral relationship.” Rouhani’s remarks in the phone call with Johnson on Wednesday did not make an explicit link between the UK non-payment of the debt and the continued detention of Zaghari-Ratcliffe, but they left that inference. The UK readout of the call focused on Johnson’s demand for her immediate release. The Iranian readout said: “Dr Rouhani also referred to the issue of Iran’s debt to the UK for several years in connection with defence purchases and said: ‘While we see that most of the countries owed to Iran are releasing blocked funds or repaying their debts, it is very strange that the process of repatriating Iran’s40-year-old defence demands has not yet made practical progress.’” Zaghari-Ratcliffe completed her five-year sentence imposed in 2016 last Sunday. Iran as a result removed the ankle tag that had kept her under a form of house arrest at her parents’ home since March, but because of the new pending charges refused to give her a passport that would allow her to return to London. No 10 said Johnson had told the Iranian president that the removal of the ankle tag on Zaghari-Ratcliffe was welcome, but “her continued confinement remains completely unacceptable and she must be allowed to return to her family in the UK”. Johnson has not been as directly in touch with Rouhani over the Zaghari-Ratcliffe case since he became prime minister although he met her husband, Richard Ratcliffe, and her daughter in Downing Street before Christmas. The call is clearly a warning shot to Iran that the UK will take some form of action if she faces further charges. He added that all British-Iranian dual nationals being detained had to be released. There are as many as three others. The Downing Street readout did not refer to any progress in the long-running conflict over the UK’s failure to pay a £400m debt owed to Iran arising out of the sale of Chieftain tanks to the Shah of Iran in the 70s. The UK has acknowledged it owes the debt, and it is understood the money has been put into a special account before a court case in April. The UK continues to insist they have not found an agreed way in which the funds can be sent to Iran without falling foul of sanctions. It acknowledges no link between the debt and Zaghari-Ratcliffe’s release. The sense in the Ratcliffe family is that the Iranians will not drop all charges on Sunday since they still regard her as a useful piece of leverage over the debt issue and wider talks about the future of the Iran nuclear deal. But Johnson’s personal intervention may help persuade the Iranians that it is not worth the risk of pressing new charges or threatening to send her back to jail. The No 10 readout 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. He [Johnson] 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.” Rouhani told Johnson: “If we are looking for diplomacy, the clear way is to lift sanctions and fulfil US commitments.” He complained that the US had not take any practical steps to lift sanctions but Iran remained committed to responding to US steps with measures of its own.