The NSS said it had contacted 233 acute and mental health trusts in the UK and found that they spent £26.72 million on chaplains from various denominations and religions.
The NSS claimed that the actual cost of chaplains in NHS hospitals, after adding building upkeep, administration and other extra costs, could be “conservatively” estimated at £40 million.
NHS guidelines say that patients should be able to hold religious services and should have access to a place to pray and a representative from their religion.
The NSS argues that funding for chaplains should come from the churches, on the grounds that chaplains are carrying out the “fundamental responsibility” of the church rather than that of the NHS.
According to the BBC, Terry Sanderson of the NSS said, "Most people who go into a hospital come from the local area and it would be better if their own vicar, priest, rabbi or imam came to see them if they felt in need of religious support.
"This could be done as part of the clergypersons' regular duties - it should not fall as a burden on the NHS."
A Church of England spokesman responded to the comments by saying, "Spiritual healthcare has long been acknowledged, by both medical practitioners and the churches, to be an intrinsic part of caring for people in hospital. NHS Trusts pay for chaplaincies because they see them as part of their duty of care to patients, not because the churches force them to."
The Government also defended the role of chaplains, with a Department of Health spokesman saying it was "committed to the principle of ensuring that NHS patients have access to the spiritual care that they want, whatever faith or belief system they follow”.
The spokesman added: "Chaplains do an extremely demanding job, often in difficult circumstances, and their skill and dedication is highly valued by patients, relatives and staff within the health service."
