The Granton Star Cause, which depicts God as a foul-mouthed drinker and includes scenes of sado-masochistic sex, has been criticised by the Church of England.
Mary Whitehouse, the lifelong campaigner against sex and violence on the screen, said the Independent Television Commission should ban the programme.
But the ITC and the Broadcasting Standards Commission said they could act only after the programme was shown and viewers had complained.
The half-hour comedy drama portrays the trials of a young man who is dropped by his football team and girlfriend and loses his job. His parents tell him to leave home because they want their privacy and when he vandalises a phone box he is beaten up by police.
To compound his misery he meets "god man" in a pub, who repeatedly swears at him and then turns him into a bluebottle.
As a fly on the wall - literally - he returns home to witness his father and mother engaging in sado-masochistic sex, which is briefly seen.
A Channel 4 spokesman said the programme would go out at 11pm in the context of renegade.tv, a late-night season of controversial "counter- culture" dramas and documentaries.
He said: "Irvine Welsh is one of Britain's leading modern day authors and reflects a specific element of our culture. It will be flagged up with suitable warnings so that people don't stumble on it unawares."
The Granton Star Cause will be shown at 11pm on 4 August.Reuse content