Demarco, who was brought up in Portobello and Leith, says his "whole life's work is in danger" after he failed to find a proper home for a collection of more than a million photographs and around 4,500 works of art.
The artist, who has attended every Edinburgh Festival and has staged exhibitions in the city since the 1950s, has expressed his dismay at the lack of support from the Scottish arts establishment in a major new documentary charting his life and work.
Rico features footage of a distressed Demarco, one of the founders of the Traverse Theatre, examining the damage done to the archive after a flood at the Summerhall arts centre, where it has been stored in recent years.
Although the National Galleries of Scotland has offered support for Demarco in the past, the archive is not expected to find a new home until a multi-million pound new collection centre is built on the city’s waterfront.
Speaking at Summerhall in the film, Demarco says: “I’ve got good reason for worry. What would happen if I weren’t here? Who would take responsibility for it and where would it go?
“My whole life's work is in danger. How many images are of great value when you consider the history of the Edinburgh Festival and the history of art?
"Who is going to bother looking at this? Do I burn this, get rid of it, because no-one’s interested in it?
“Nobody comes here, no-one gives a damn about it. This is the only archive of the Edinburgh Festival you’re going to find.”
The documentary tells of Demarco’s fears the archive will end up “locked away” and not easily accessible, rather than an educational resource.
Demarco is asked by Sir John Leighton, director-general of the National Galleries of Scotland, what he would like the future of his archive to be.
Demarco responds: “I don’t have a five-year plan. That would be foolish.
"We’ve inherited a culture where art is now used self-destructively as part of the world of tourism.
"I can see that I’m going to be ending my life, if I’m not very careful, swallowed up in this nonsense.
"Art has been commodified so that unless it is about profit it is not taken seriously by our local or national government masters.”
Speaking in the documentary, Summerhall founder Robert McDowell says: "Even though he [Demarco] has an archive now worth many millions in theory the world is always moving on.
"The practice of how gallerists operate and the context of how artists put on shows is quite changed from how it used to be.”
However, actor Brian Cox tells Demarco: “What is so extraordinary about you, and absolutely no-one can beat you on this, is the detail.
"You’ve detailed everything to such an extent that it [the archive] is so unique. As far as I know, no-one has actually detailed every phase of modern, post-war cultural history. That’s an astonishing achievement.
"That’s your legacy. What people will eventually realise, if they want to know about how things were, they will go to Demarco because he’s the guy who marked it all the way along the line.”