Barman Steven Relf, 40, was jailed indefinitely after admitting raping two women he targeted when he served them drinks in a pub.
Police branded him a "sexual predator" and said he could have had as many as 40 victims.
In a letter to an inmates' magazine, Relf wrote: "I recently had the displeasure of sharing a cell with a Bible-thumping believer."
A source said Relf was "furious" at having to share at Manchester Prison with the Christian convict and wanted him to be "evicted".
He said: "He moaned about how the guy wouldn't shut up about God. He said he wanted to speak to a lawyer about his rights so he could be moved cells."
The other inmate was later transferred.