A reality Tv star has threatened legal action and demanded an apology over the publication of a false rumour linking her to rapper Jay Z.

Casey Cohen, who featured in U.S. series Princesses: Long Island, has issued a cease and desist letter to a number of media outlets dismissing a false story about a romance with the hip-hop star as a "foul and phoney mistress-rumour".

The document, obtained by editors at Tmz.com, demands an apology and asks for the incorrect story to be removed from the Internet.

Jay is married to singer Beyonce.