For over 15 years, Jeffrey Epstein served as a close personal adviser to Leslie H. Wexner, the billionaire mogul behind Victoria’s Secret and Bath & Body Works. Now, Mr. Wexner says Mr. Epstein “misappropriated vast sums of money” from him and his family.

Mr. Wexner, the chief executive of the retail giant L Brands, included the accusation in a 564-word letter he sent Wednesday to the Wexner Foundation, giving his most detailed account yet of how his life and affairs became intertwined with Mr. Epstein, who was arrested last month and charged with sex trafficking involving girls as young as 14.

In the letter, Mr. Wexner said the misappropriation was first discovered in 2007 as he separated from Mr. Epstein. In early 2006, Florida authorities charged Mr. Epstein with multiple counts of molestation and unlawful sexual activity with a minor. In 2008, he pleaded guilty to state charges of solicitation of prostitution from a minor and was required to register as a sex offender.

“It was agreed that he should step back from the management of our personal finances,” Mr. Wexner said in the letter. “In that process, we discovered that he had misappropriated vast sums of money from me and my family. This was, frankly, a tremendous shock, even though it clearly pales in comparison to the unthinkable allegations against him now.”