In 1955 he fell out with Maria Callas during the performances of Medea at the Rome Opera and in 1961 his contract with La Scala was terminated after an open conflict with fellow Bulgarian Nicolai Ghiaurov whom Christoff blamed for collaborating with the Bulgarian communist regime.
En 1955, pelexou con Maria Callas durante as interpretacións de Medea na ópera de Roma e en 1961 o seu contrato con La Scala rematou tras un conflito aberto co seu colega búlgaro Nicolai Ghiaurov a quen Christoff culpou de colaborar co réxime comunista búlgaro.