A former drug dealer who was given a whole life sentence after killing four people, including two female police officers, has reportedly turned to God behind bars.

Dale Cregan shot and killed 23-year-old Mark Short on 25 May 2012 and followed his murder shortly after with that of Short's father, David, 46, on 10 August 2012.  

On 18 September that year, Cregan made a fake emergency call to the police and proceeded to kill Constables Nicola Hughes, 23, and Fiona Bone, 32, when they arrived on the scene.  

Insiders at Strangeways in Manchester, where the one-eyed killer is being held, say he is attending chapel regularly and has been seen holding a rosary, The Mirror reports.

However, his supposed faith has been taken with a pinch of salt by one insider who told the newspaper Cregan was one of a "small group of regulars" at the prison chapel.

"It was a surprise at first but now it's become accepted. It is fair to say his motives have been questioned by some," he said.

"The idea of him being a man of God is laughable. No one believes it but the church does not turn people away."

Another source told the paper that there seemed to be more prisoners taking an interest in going to chapel in recent months.

"It could be his influence, no one's sure," the source said. "But the authorities will be keeping an eye on things to make sure there is no conflict between the faiths."