The Tehran-based family of the executed British-Iranian dual national Alireza Akbari have been prevented from seeing his body or burying him in the grave in which he had asked to be laid to rest in Shiraz, his birthplace, family members have told the Guardian. Akbari was executed for spying for M16, charges he vehemently denied and for which there is no substantive evidence, save a confession extracted under torture. In a final humiliation for the family, Akbari’s sister and daughter went to the Tehran cemetery where the officials had said he must be buried to collect the body, and to place him in the allocated grave site, only to be told by officials that a man with the same name and details had been buried at the cemetery on Thursday, and there was no body to collect. Reports had circulated briefly on Thursday that Akbari had been executed, only for the reports to be swiftly denied. The family were told he would not be executed on Friday, a holiday in Iran, and say they were also given false hope on Friday evening by the intelligence ministry that there was a chance of reprieve, only to wake on Saturday morning to a statement from the judicial news agency announcing he had been executed. Negotiations then began over the collection of the body, but the family were required to sign a statement that he would only be buried quietly in a specific marked grave in the Tehran cemetery. Any attempt to take the body to Shiraz would lead to it being seized and destroyed, the family were advised. But on Monday the family arrived to bury Akbari in the agreed plot, only to be told by cemetery officials that a body with the precise same name and details had been buried there on Thursday. A video of the burial had been made but then taken away, the officials said. A distraught member of the family not resident in Iran said: “We have never seen the body. We do not know if he is in that grave site. We do not know if he was executed on Thursday or Sunday, or even if the talk of parole was just to string us along. Perhaps even we do not know if he is dead or alive, because we cannot access the grave.” Through tears, the family member said: “They are just playing with us. It is cruel and heartless. They have tried to destroy his reputation by fabricating that he is a traitor, and now this.” News of Akbari’s treatment was confirmed by Andy Slaughter, the MP for Hammersmith and the constituency MP for the Akbari family. Slaughter called for Akbari in death, if not in life, to be treated with dignity and respect. The foreign secretary, James Cleverley, making a Commons statement, said the news filled him with revulsion, describing it as “deeply distressing”. He told MPs that Akbari had been tortured to make him confess to spying, saying: “He fell victim to the political vendettas of a vicious regime … [the Iranian government] thinks nothing of using the death penalty to silence dissent and settle internal scores.” He revealed that the Akbari family had first contacted the Foreign Office in February last year, and had been receiving support since then. Apart from imposing sanctions on the Iranian prosecutor general at the weekend, he said, 40 sanctions had been imposed on the regime since October, including against six individuals linked to the revolutionary courts. He said he had already met the UK ambassador to Tehran, Simon Shercliff, and promised the steps taken so far would not be the limit of the UK response. He refused to speculate on the proscription of the Islamic Revolutionary Guards corps, but the bulk of the MPs that intervened during his statement called for him to act.