Britain has warned its citizens against all travel to Iran just days after it was revealed a British Council worker had been jailed for spying.
On Friday, Britain’s Foreign Office said its citizens, particularly dual nationals, face “an unacceptably higher risk of arbitrary detention and mistreatment than nationals of many other countries”.
It comes after London-based British Council worker Aras Amiri, an Iranian national, was jailed in Iran for 10 years for being a UK spy.
She was detained in March while visiting a sick relative.
The move also follows the case of British-Iranian dual national Nazanin Zaghari-Ratcliffe, who has been detained in the country since 2016.
Foreign Secretary Jeremy Hunt said: "Dual nationals face an intolerable risk of mistreatment if they visit Iran. Despite the UK providing repeated opportunities to resolve this issue, the Iranian regime's conduct has worsened.
“Having exhausted all other options, I must now advise all British-Iranian dual nationals against traveling to Iran. The dangers they face include arbitrary detention and lack of access to basic legal rights.
“Regrettably, I must also offer a message of caution to Iranian nationals resident in the UK – but who return to visit family and friends – especially where the Iranian government may perceive them to have personal links to UK institutions or the British government.”
Officials said the Iranian government does not recognise dual nationality and its capacity to provide consular support is “extremely limited”.
On Friday, Iran's ambassador to the UK Hamid Baeidinejad tweeted: "If, as Iranian dual national or as Iranian national working in the UK, you are not collaborating with intelligence agencies and/or not collecting classified information for them, you may safely travel to Iran without any anxiety and are under full protection by law in Iran.
"Every day thousands of Iranian dual nationals and Iranian nationals working in the UK are travelling safely to Iran. Iranian dual nationals and Iranians working in the UK are all respected Iranian citizens and are all welcomed to visit their country and families."
The family of Ms Amiri only discovered she had been sentenced on Monday through local media.
Her cousin Mohsen Omrani told The National she was being "held hostage" by the Iranian regime, who were using her as a bargaining chip in political negotiations with the British government
“She’s a bargaining chip. She doesn’t even have a British passport,” he said. “Essentially they are asking for a ransom.”
Ms Amiri has a fiancé based in the UK, who has been unable to get a visa to visit her in Iran since her arrest.
She is being held Tehran’s notorious Evin Prison, where Ms Zaghari-Ratcliffe is also an inmate.
British Prime Minister Theresa May on Wednesday described her sentencing as "utterly shocking" and said the government was "deeply concerned".
The sentencing comes amid tensions between Iran and Britain over the fate of British-Iranian mother Ms Zaghari-Ratcliffe who was arrested by Iranian authorities in 2016 as she was leaving Tehran.
Zaghari-Ratcliffe, who worked for the Thomson Reuters Foundation, was put on trial and is now serving a five-year jail sentence for allegedly trying to topple the Iranian government.