Knox fails to clear her name in slander retrial.

Amanda Knox has lost her bid to overturn a slander conviction in relation to the 2007 murder of British student Meredith Kercher after an appeals court in Florence upheld the ruling on Wednesday.

American Knox, 36, spent four years in prison in Italy after being convicted of the murder of 21-year-old Kercher, before being cleared of the crime in 2015 along with her Italian former boyfriend Raffaele Sollecito.

Knox had returned to Italy this week in an attempt to quash a three-year defamation conviction for falsely accusing Congolese bar owner Patrick Lumumba of killing Kercher.

Lawyers for Knox claimed that she had been under police duress when she named Lumumba who was jailed for two weeks in 2007 before being released.

Knox, who attended the hearing in Florence with her husband, will not serve any time in prison however as the sentence takes into account the time she already served in jail.

Earlier this week she said she was hoping to clear her name "once and for all of the false charges against me."

Her lawyer Carlo Dalla Vedova told reporters on Wednesday that Knox was "very upset" at the ruling, adding that her legal team was "very surprised at the outcome".