Ofcom, the new TV and telecommunications regulator, is expected to launch a fresh investigation into the commitment to religious programming on ITV and Channel 4.
It wants to examine the financial commitment of the broadcasters to the "God slot" amid fears they may be paying little more than lip service to their public service requirements.
Richard Hooper, the deputy chairman of Ofcom and the head of the influential content board that will regulate what goes out on radio and TV, said public service obligations must take "centre stage" in the life of the new regulator.
"Public service broadcasting will be a key policy issue at the centre of Ofcom's concerns. But as a converged regulator, merging economic and content regulation, we will always be looking at a topic like this both from an economic as well as cultural point of view," he added.
"We all need to remind ourselves that public service obligations have to be financed."
It is understood that short programmes such as Channel 4's The Hajj have underlined Mr Hooper's suspicion that the amount invested into religious programming may be a more important indicator of quality than strict "hours and minutes" quotas.
The series of 10-minute films, produced for Channel 4 by ITN, followed six Muslims on their once-in-a-lifetime trip to Mecca, and was broadcast on peak time television after the Channel 4 News.
The unique conditions, including hiring an all-Muslim film crew, filming around the clock and sending footage by courier to Jeddah where the films were edited, meant the series cost over £630,000 to produce.
The programme got up to 1.6 million viewers - a respectable audience for a religious slot.
Channel 4 has agreed to provide one hour of religious programming a week as part of its licence, which is heavily influenced by its remit for cultural diversity.
Other programmes in Channel 4's religious line-up for 2003 include a discussion programme hosted by the new Archbishop of Canterbury, Dr Rowan Williams, and live coverage of the marching season in Northern Ireland.
At present ITV is required to provide two hours a week of religious programming.
In its statement of programming policy for 2003, the channel pledges to meet this exactly by devoting 104 hours to religious programmes, mainly on Sunday mornings and late evenings.
The bedrock of its commitment is the Sunday morning show, My Favourite Hymns. Other documentary and discussion programmes include a new series about the Alpha course - a controversial scheme to introduce people to Christianity, a series titled Sex and Religion, and John Meets Paul: a Mediterranean Journey, in which presenter John McCarthy follows the journeys of St Paul.