A disabled Pakistani Christian was forced into a confession of blasphemy because he could not bear to watch his wife being tortured, he says.

Shafqat Emmanuel and Shagufta Kausar, from Gojra in eastern Pakistan, were found guilty in 2013 of sending a text message "blaspheming" against the prophet Mohammed to local Muslims and sentenced to death.

According to the Christians in Pakistan website, they were both tortured by police. Shafqat, who is paralysed from the waist down, told lawyers from aid organisations: "There is no man who can stand to see his wife being tortured by police, so to save my wife, I confessed."

The couple, who have four children and work at St John's School in Gojra, have denied sending the texts, saying they had lost the mobile from which the texts came and that the SIM card in it was not theirs.

"There was no evidence that the text messages came from a phone owned by the couple," Farukh Saif, an official of World Vision in Progress, which is helping them, told Christians in Pakistan.

"In the first place they had lost the phone some months before July 2013 and secondly there was no SIM card in their names.

"The only evidence police produced was a bill for a SIM card from a shop owner which is unheard of."

Shafqat has appealed at Lahore High Court, seeking bail due to his deteriorating health condition. "I have developed bedsores and I may die in jail as there is no possibility of a better treatment there," he said in his petition.

Pakistan's notoriously harsh blasphemy law has been widely discredited. It is used to settle private scores and courts are reluctant to acquit those accused as mob violence is often the result. Accusations are made with little or no evidence produced.

Attempts to modify the law have been unsuccessful, with prominent politicians Salman Taseer and Shahbaz Bhatti both murdered for their opposition to it. More than 60 people charged with blasphemy have been murdered before their trials were over.

While no one has been executed for blasphemy, those found guilty face the prospect of life in prison.