Religious groups should fund their own presence in UK hospitals and save the NHS some £40m per year, the National Secular Society (NSS) suggests.
The organisation of non-believers says such money would be better spent on "much needed" nurses or cleaners.
The NSS claims even organ players in hospital chapels are on NHS payrolls.
NHS guidance notes all patients have a right to religious observance and that trusts should provide both faith representatives and places to pray.
However, the Catholic Church in Scotland said it agreed that spiritual carers should not be funded by the NHS.