He told ITV's Good Morning Britain programme on Monday that his relationship was "obviously quite incompatible" with his position as party chief.
He went on to say that while the "romantic" side of their relationship had ended, he would continue to support Ms Marney's family who he described as "distraught" over the revelations.
In a series of text messages sent to a friend, Ms Marney said that the Prince's "black American" fiancee will "taint" the Royal family with "her seed" and pave the way for a "black king", according to a report by the Mail on Sunday.
The 25-year-old, who describes herself as a model, actor, journalist and Brexiteer on her Twitter profile, also reportedly said Ms Markle had a "tiny brain" and that black people were ugly.
She has since been suspended from the party.
More follows..