Former escort Madison Ashton has lost her appeal against the estate of billionaire Richard Pratt, who she says promised her millions.

Ms Ashton launched an appeal against the decision in 2012 to reject her bid against the cardboard king’s estate.

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Madison Ashton quit the escort business to be Pratt’s mistress. Photo: AAP

Ms Ashton said Mr Pratt had promised to set up two trust funds, worth $2.5 million each, for her two children and pay her $500,000 as a “retainer” to stop working as an escort and become his mistress.

Although the Supreme Court agreed the pair had the conversation, it found Ms Ashton’s acceptance of $100,000 and the transfer of car into her name was done in full satisfaction of the trust claim.

In November 2005, Ms Ashton signed a document from a Visy Industries employee that released Mr Pratt from any financial responsibility in exchange for a payment of $50,000 to the former mistress.

Mr Pratt died in 2009.