The father of an Irish man who has been detained in an Iranian jail since last October will hand over a petition calling for his son's release to the Iranian Embassy in Dublin on Thursday.

Bernard Phelan, 64, from County Tipperary, was jailed during the widespread protests against the Iranian Islamic regime and has been sentenced to six-and-a-half years in prison. 

Phelan, who works for an Iranian tour operator, was arrested for taking a photograph of a mosque in the Iranian city of Mashhad during the widespread protests against the regime, which has seen millions of Iranians take to the streets. He was promoting Iran as a tourist destination at the time of his arrest. 

He has strongly denied the charge of helping to incite propaganda against the Iranian government in Tehran. 

His father Vincent, who is 97, said his son is seriously ill in prison and urged the Iranian authorities to release him, adding that Bernard did nothing wrong. 

"I can’t understand why they put Bernard in prison. Bernard didn’t do anything wrong. I miss him a lot and I’ll miss him more every day. I am relying on him to look after me," Vincent Phelan said in a YouTube video recorded by the Phelan family. 

"I have lost one son and I have only one left – Bernard. For the next few years – I don’t know how long I am going to live. Who does? But I rely on Bernard to help me. He (Bernard) was hoping to get home soon. I hope the Government are putting pressure on the Iranians." 

Caroline Massé-Phelan, Bernard's sister, added that the family intends to hold a vigil outside the Iranian Embassy on Thursday, March 30, amid concerns about Bernard's fragile condition. 

"He is extremely fragile. His physical health is declining rapidly. He has several health issues, cardiac and bone issues. But also he is going blind because he had an operation last summer, which was fine and went well, but it hasn’t been treated so he can’t see very far anymore. He is very concerned that that won’t be repairable when he comes home," Massé-Phelan told RTÉ's Colm Ó Mongáin.

Massé-Phelan also said her brother was in the "wrong place at the wrong time", stating that he is being used as a pawn in a political game. 

"When he traveled he had no idea that these protests would escalate and that his life would be in danger. He was hauled off to the street and into a van, and taken away. He is not alone in being one of these hostages being kept in Iran as some sort of pawn in a political game going on in the country." 

She said her brother is afraid and depressed, adding that he doesn't see a way out. 

"He understands that the (Irish) Government is in close contact with the Iranians, but he doesn’t see the fruits of that."

The Phelan family hopes to collect 5,000 signatures before arriving at the Iranian Embassy on Thursday evening when Vincent Phelan will hand over the petition to Iranian authorities.