The Congolese bar owner falsely accused of killing Meredith Kercher has said the decision to quash the conviction of Amanda Knox was a triumph for being “American and rich” rather than for justice.

Patrick Lumumba, 42, said the surprise ruling by Italy’s supreme court to annul the murder convictions of Knox and her former boyfriend, Raffaele Sollecito, was motivated by political and diplomatic reasons.

He told the Observer: “This is not good for justice, I think it shows the power available for rich people – she’s American and rich. For a country like Italy this is not good. I think there were diplomatic problems with the US and it makes things difficult with the US so they let her free.

“Amanda is free because she is American, but Americans are human like everybody.”

Lumumba was arrested in November 2007 and spent two weeks behind bars after Knox told Italian police he had killed 21-year-old Kercher, from Coulsdon, Surrey. Kercher’s throat was slashed and she had been sexually assaulted while she was on an Erasmus year in the medieval hill town of Perugia.

At the time Knox, now 27, told investigators that she had “covered her ears as he [Lumumba] killed” Kercher in the bedroom of the flat the two women shared.

Knox’s claim – which Italian prosecutors alleged was intended to direct suspicion away from herself – was later proved to be false and Knox was given a three-year sentence for it. She has since admitted to struggling with guilt over the false accusation.

But Lumumba, who said his life and business were ruined by the allegation, said: “Amanda lied to me. I am feeling very bad [about the acquittal].”

Speaking from Krakow in Poland, where he now lives with his wife after losing his bar in Perugia and struggling to find a job in the wake of the false murder accusation, Lumumba said that despite the final ruling, he still believed Knox held the answer to the case.

“What Amanda did I don’t know, but I think she knows why Meredith died.”

Knox and Sollecito have always maintained their innocence and Friday’s decision by the court of cassation marks the end of a lengthy legal battle.

Kercher’s mother, Arline, said she was “surprised and shocked” at Friday’s ruling and added it was too early to know what the family would do next. They had previously expressed confidence in the Italian justice system.

Before Friday’s verdict it had been widely anticipated that the court would order a retrial, even if it overturned the previous convictions. The decision by the five-judge panel to clear the pair definitively ends the long-running saga.

Speaking outside the courtroom on Friday, the family’s lawyer, Francesco Maresca, said: “The judges said there is a lack of proof and whoever acted with [Rudi] Guede [the only person found guilty of the murder] has not been found.” Guede, from the Ivory Coast, is almost halfway through a 16-year prison sentence after his trial was fast-tracked in 2008.