The family of a Dubai-based business executive who has spent five years in a Tehran jail on contrived charges has urged world leaders to snub the Iranian regime unless it frees its ‘hostage’ prisoners. Siamak Namazi, the longest held US-Iranian dual national in Iran, marked both his 49th birthday and his 1,800th day in detention this week. He was arrested in 2015 and convicted of collaborating with a hostile government. As world leaders prepare to speak at the UN General Assembly, his brother Babak Namazi told <em>The National</em> that the "international community should make it clear that they will not tolerate any longer this hostage diplomacy". He added: “If Iran wants any recognition or legitimacy, it has to act as a responsible member and that starts with basic human treatment of people of all nationalities.” US President Donald Trump is set to address Iran in his speech to the General Assembly on Tuesday after declaring that all international sanctions against Iran have been restored. His Secretary of State Mike Pompeo tweeted his support for the campaign to free Mr Namazi last week and said that world leaders should refuse to meet his Iranian counterpart Javad Zarif until all wrongfully detained foreigners were released. Germany cancelled a visit by the foreign minster last week after the execution of a wrestler who joined anti-government protests. “There must be consequences for the Iranian regime’s barbarity,” said Mr Pompeo. Mr Namazi, an oil company executive, was arrested in 2015 as he prepared to travel home to Dubai after a short family visit to Iran. A UN body in 2017 ruled that he had been held illegally by Iran because of his nationality. His supposed crimes included joining hundreds of people - including Iranian officials – at conferences, according to his family. His father, Baquer, a retired former UN worker now aged 84, was arrested the following year as he arrived in the country to visit his son. Both men were sentenced to a decade in prison. Iranian media have spread lurid theories that the pair was involved in smuggling tainted birth control pills to reduce the population size. “The claims are just so outrageous,” said Babak Namazi. “It’s so ridiculous and so cruel.” Siamak Namazi spent more than half of the five years he has so far served of his sentence on a ward controlled by the Islamic Revolutionary Guard Corps (IRGC) where he was mistreated and tortured, say his family. For the first year he was kept in custody, his father was behind a wall ten metres away but the pair were never allowed to see each other. Baquer Namazi has since been released because of serious health problems that required heart surgery. He requires further treatment but has been barred from leaving Iran. Siamak Namazi has been told repeatedly that he was eligible for temporary release but promises of freedom have been repeatedly dashed. “What my brother wants to say is don’t forget us as victims of an unjust process,” said Babak Namazi. “He is part of this select group … who don’t want to be engulfed in darkness. That’s how they feel right now. “He is desperate as we are. My family is being used for whatever political gains the Iranians think they can get. “I don’t understand this – my family doesn’t understand this – how we got caught up in a political chess game.” Iran does not recognise dual nationals and there are no exact numbers of how many are being held, owing to the sensitivity of the information. They include British-Iranians Nazanin Zaghari-Ratcliffe, 41, a charity worker, and Anoosheh Ashoori, 66, a retired engineer. The family of Mr Ashoori is now working with lawyers to persuade the government to grant him diplomatic protection and give his detention greater status at a government level. The UK government has already granted the protection to Ms Zaghari-Ratcliffe. Her family said that move was responsible for the cancellation of a new trial last weekend after the British embassy sought to attend her trial. Sherry Izadi, Mr Ashoori’s wife, said: “It would give this case a degree of official recognition and more help for Anoosheh in Iran. “We want to make the case more important for both governments.”