On Wednesday Prosecutor General Giovanni Galati, who successfully appealed the pair’s acquittal, said that Italy’s highest court had “substantially demolished the second-instance judgement” in its decision to release Sollecito and Knox, La Nazione Umbria reported. “A sentence that could not be undone was obviously flawed,” he added.

Francesco Sollecito, the father of the accused Italian, said the statements made by Galati were “unorthodox and improper”, the newspaper said.

“This is still an open process”, Sollecito said ahead of his son's retrial, which is expected to take place either later this year or early next year.

Italy’s supreme court released a 74-page document earlier this month detailing its reason to reverse the pair’s acquittal, citing "numerous examples of shortcomings, contradictions and incoherencies".

Knox and Sollecito were freed on appeal in 2011, four years after Kercher was murdered in Perugia, ending their 26- and 25-year prison sentences.

A third person, Rudy Guede, remains in prison for the murder after his appeal was rejected.