Coolidge insists she should have received publishing royalties for the rock classic, which was recorded by Clapton under the name Derek and the Dominos.
In her soon-to-be-published memoir, Delta Lady, the star claims she had a significant hand in writing Layla, but was never credited, and the royalties were split between Clapton and co-writer Jim Gordon.
In an excerpt from the book, published by the Miami Herald and obtained by UltimateClassicRock.com, Coolidge states she and Gordon, who were once lovers, collaborated on a song titled Time (Don't Let the World Get in Our Way). The track was played for Clapton.
"I remember clearly sitting at the piano at Olympic Studios while Eric listened to me play it all the way through," she wrote. "Jim and I left a taped cassette of the demo with Eric, hoping of course that he might cover it. Nothing came of it and I largely forgot about it."
She later realised Eric had recorded her song when she first heard Layla.
"I was infuriated," she recalled. "What they had clearly done was take the song Jim and I had written, jettisoned the lyrics and tacked it to the end of Eric's song. It was almost the same as the arrangement."
Coolidge fought for credit but it was never given, and she kept silent about the drama until now.
"There was no way Jim could have forgotten we'd written the song together," she added. "And, frankly, I don't think Eric could have either."