She insisted that Guede had “acted alone” in murdering Ms Kercher.

But Italy’s Supreme Court ruled that the Leeds University student was killed by more than one person, with the other aggressor or aggressors remaining unidentified.

“Were he actually to acknowledge his responsibility, it would bring closure to the Kercher family, it would end the murky speculation around this case, it would restore my wrongly damaged reputation and that of Raffaele.

“Today Rudy’s free, and he has yet to tell the truth, allowing others to continue bearing the burden of his guilt,” Ms Knox wrote. “Guede could do all that right now. He could ask for forgiveness.”

Ms Knox, from Seattle, and her then boyfriend, Raffaele Sollecito, were initially accused of murdering Ms Kercher and found guilty at their first trial in Perugia.

They both spent four years in prison. After a years-long legal saga they were subsequently acquitted by the Supreme Court in Rome.

Ms Kercher, 21, from Coulsdon in Surrey, was murdered in November 2007. She was on a year’s study abroad in Perugia, a popular destination for foreign students.

While Ms Knox says she was falsely accused by Guede, she in turn falsely accused her then boss of the murder of Ms Kercher.

She told police during her initial questioning that the murder had been committed by Patrick Lumumba, a Congolese man who ran a pub in Perugia.

He spent nearly two weeks in prison before being cleared of any involvement in the crime.