Darlene Lutz, a former friend and art consultant of Madonna’s, consigned to auction various items the star was unaware were no longer in her possession, including a pair of underwear, several personal photos, an old checkbook and multiple letters, one sent by Tupac and another in which the she supposedly calls Whitney Houston and Sharon Stone “horribly mediocre”.

The auction house released a statement to Reuters calling Madonna’s attempts to halt the sale “completely baseless and meritless”, adding that they believe “her intent is nothing more than to besmirch the good reputations of the auction house and Ms Lutz”.

The singer and Tupac briefly dated in the 1990s before the legendary rapper’s 1996 death at the age of 25 in a drive-by shooting in Las Vegas.

In the break-up letter Tupac writes: “For you to be seen with a black man wouldn’t in any way jeopardize your career – if anything it would make you seem that much more open and exciting. But for me, at least in my previous perception, I felt due to my ‘image,’ I would be letting down half of the people who made me what I thought I was. I never meant to hurt you.”

In another letter addressed to “J,” believed to indicate the actor John Enos with whom Madonna also had a brief relationship, she writes that “it’s so unequivocally frustrating to read that Whitney Houston has the music career I wish I had and Sharon Stone has the film career I’ll never have”. It continues, “Not because I want to be these women because I’d rather die, but they’re so horribly mediocre and they’re always being held up as paragons of virtue and some sort of measuring stick to humiliate me.” The letter was expected to fetch up to $5,000.

In court documents, Madonna alleges that Lutz “betrayed my trust in an outrageous effort to obtain my possessions without my knowledge or consent.” Gotta Have It! Collectibles and Lutz have stated they will challenge the Like a Virgin singer’s claims in court.

The auction is slated to begin on 19 July, with many of the items, including old articles of clothing, jewelry, and lyric sheets, still available.