Pastors Behnam Irani and Matthias Haghnejad, and Deacon Silas Rabbani, who had earlier had capital charges against them dropped, each received six-year sentences in October.
Their lawyer, Vahid Moshkani Farahani, said that he is only allowed to meet with his clients on the day of the trial; multiple requests to meet with them beforehand were rejected, according to Christian Solidarity Worldwide.
He has also expressed concern about the welfare of Pastor Behnam Irani, who is unwell and has been deprived of adequate medical care.
The additional six-year sentence handed to Pastor Irani means he will serve a total of 12 years in prison.
He was initially arrested in December 2006, and sentenced in 2011 to six years imprisonment for "action against the state" and "action against the order." Whilst in prison his health has deteriorated.
Critics of the regime say its another example of persecution against religious minorities in the Islamic State.
CSW's Chief Executive Mervyn Thomas said, "It is unacceptable that these men have been denied access to their legal counsel ahead of the court hearing. We remain concerned about the lack of due process in their case and the exceptional nature of their punishment.
"They have committed no crime and are effectively being punished for their faith. We are deeply concerned for their wellbeing and in particular for Pastor Irani's health, which has deteriorated significantly during his unjust detention.
"We urge the Iranian authorities to release these men and the many others who are being held in contravention of the international covenants guaranteeing freedom of religion or belief to which Iran."
