The former Bishop of Rochester has written to Iranian President Mahmoud Ahmadinejad to ask that he grant clemency to a pastor sentenced to death for apostasy.

Pastor Youcef Nadarkhani has been held in Lakan Prison, Rasht, since being found guilty of apostasy in September last year and sentenced to death, despite there being no such crime under Iran’s penal code.

In his letter, Bishop Michael Nazir-Ali asked President Ahmadinejad for his "urgent intervention" to save Pastor Nadarkhani.

“It appears that the court who sentenced Pastor Nadarkhani has chosen to impose a sentence which is beyond what is codified in the Iran Penal Code and contravenes both the International Covenant on Civil and Political Rights (ICPPR), and article 23 of the Iranian constitution," he said.

“Although the court has justified these actions we ask you to appeal to the Iranian Government to have compassion on Pastor Nadarkhani and grant him clemency.

“Iran has a long tradition of justice and of compassion and we appeal to the Iranian authorities to uphold this tradition in Pastor Nadarkhani’s case.”

Pastor Nadarkhani was told that the death sentence would be annulled if he recanted his faith and returned to Islam. In appeal hearings, however, the pastor has refused to give up his Christian faith.

There are concerns that the execution will go ahead after the Fars News Agency reported this week that the pastor is now standing trial for rape, extortion and security-related crimes rather than apostasy.

The news agency quoted the Deputy Governor-General of Gilan province, Golam-Ali Rezvani, as saying that Pastor Nadarkhani was a “Zionist” and “traitor” who had “committed security crimes”.

The pastor’s death sentence has been condemned by Foreign Secretary William Hague and human rights groups, including Christian Solidarity Worldwide and Human Rights Watch.

Mr Hague said the sentence demonstrated the Iranian regime’s “continued unwillingness to abide by its constitutional and international obligations to respect religious freedom”.

“I pay tribute to the courage shown by Pastor Nadarkhani who has no case to answer and call on the Iranian authorities to overturn his sentence,” he said.