An extraordinary propaganda film released by Iran’s hardline Revolutionary Guards has revealed deep splits between the country’s parallel intelligence agencies and suggested that imprisoned dual nationals could be victims of the infighting.

At least 30 dual nationals, including the British-Iranian woman Nazanin Zaghari-Ratcliffe, are estimated to remain behind bars in Iran, mostly on national security charges, including spying.

The Iranian motives behind such arrests have been unclear, as have been the political machinations over them. But the new film, made in the style of a documentary, sheds light on the tug of war between hardliners dominating the unelected faction of the Iranian establishment and the elected faction represented by the moderate administration of President Hassan Rouhani.

The 21-minute film, produced by the intelligence arm of the Islamic Revolutionary Guard Corps (IRGC) and shown to Iranian parliamentarians and released online, explores the case of Canadian-Iranian Abdolrasoul Dorri-Esfahani, a member of Iran’s nuclear negotiating team jailed for espionage.

The film amounts to an extraordinary attack by the IRGC’s intelligence arm on Rouhani’s ministry of intelligence, which insists Dorri-Esfahani is innocent. It is believed to be the first time such a spat between Iranian intelligence services has been aired in public.

Rouhani’s top media aide, Hesamoddin Ashena, hit back at the film on Twitter, saying its release was “very dangerous” because it brought to public attention an “institutional rivalry” between the two intelligence services.

Ashena’s intervention also made clear that Rouhani’s government opposed the arrest of a number of other dual nationals, including environmental activists.

The latest report by the UN special rapporteur on Iran submitted in March urged Iran to address concerns about the imprisonment of dual nationals, which it said, “represent an ongoing pattern of deep concern and emblematic examples of due process failings”. The UN report said the cases against dual nationals were “related to the mere suspicion of anti-state activities with no detailed charge sheets made available nor any victim specified in any of the offences”.

The Revolutionary Guards, allied with the hardline judiciary, are behind the arrests of dual nationals. Both institutions act independently of Rouhani’s government and are shielded by the country’s supreme leader, Ayatollah Ali Khamenei.

Dorri-Esfahani, an adviser to the governor of Iran’s central bank, oversaw talks about the financial aspects of the 2015 nuclear deal. Dorri-Esfahani was arrested by the guards just before boarding a flight destined for Canada and is now serving a five-year jail term.

The IRGC’s assessment is that Dorri-Esfahani had been spying. The film reveals no incriminating evidence of espionage under Iranian law but does portray him as instrumental in making sure the nuclear agreement was struck. That agreement is now on life support because of Donald Trump’s decision to pull the US out of it.

Hardliners in Iran have long been resentful of the deal and believe it was a way for the west to infiltrate Iran. Clips of Khamenei warning against enemy plots to infiltrate the country and its decision-making process feature prominently in the film.

“One of the aims of these countries was to put an infiltrating agent inside our negotiating team,” the documentary says of Dorri-Esfahani, presenting his case as “one of the most complex spying cases” Iran has ever seen. The film also features what it portrays as Dorri-Esfahani’s confessions.

“Why was a dual national appointed to oversee the most important part of the talks, about the the financial and economic issues?” the documentary asks, accusing the former negotiator of providing sensitive economic information to Iran’s enemies through working with multinational firms such as PwC, which the documentary said, in an unfounded allegation, had links with UK and US intelligence.

“A month after Dorri-Esfahani joins the team, in an unbelievable development the agreement is reached,” the film adds.

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Ali Vaez, the director of the Iran project at anti-war organisation the International Crisis Group, said the documentary showed that the rivalry between parallel intelligence agencies and factions was becoming more bitter and more public.

“In the threat that Trump poses to Iran, the IRGC sees an opportunity to bolster itself and weaken its political and institutional rivals, painting them as too compromising or compromised. This will allow the IRGC to increase its dominance in the security and economic spheres at the expense of more pragmatic forces of Iranian politics,” he said.

“The IRGC’s intelligence branch is as conspiratorial as the Intelligence Ministry [of Rouhani’s government] is professional. Dual nationals fit the profile of the IRGC’s favourite conspiracy theories and become pawns in a power struggle between the hardliners and the more pragmatic forces of Iranian politics.”

The film said that “the Islamic Republic has been more harmed by dual nationals than anyone else”, but Vaez said “at some point the Islamic Republic will have to acknowledge that just like [the secret police force] Savak under the shah, their security apparatus is doing them more harm than good”.