The former Australian Miss Universe representative joined the show as Sienna Cammeniti last year. She will be seen on UK screens for the first time later this month.
McNaught was brought in by the soap's chiefs in a bid to boost flagging ratings in Australia. They also recruited bikini model Imogen Bailey (Nicola West) and former Australian Idol contestant Dean Geyer (Ty Harper).
However, sources have told the Herald Sun newspaper that Erin "seemed to be counting down the days" until her contract expired. She has now returned home to Sydney.
Natalie Blair (Carmella Cammeniti) and Pippa Black (Elle Robinson) are also leaving the soap later this year.