Litvinenko had left Russia six years ago and held UK citizenship. He was a critic of Kremlin policy.
Investigations into the cause of death revealed that traces of Polonium 210 were found in Litvinenko's urine.
Scaramella, a professor at the University of Naples, said he was not looking for police protection.
"But there is no doubt it was the Kremlin," he said.
"And as I am the only one to have collected all his information ..." He left his statement unfinished.
According to British media, Scaramella met with Litvinenko in a London sushi restaurant on November 1.
Scaramella showed Litvinenko emails indicating that the FSB, the successor to the KGB, was considering using force against critics of Vladimir Putin, Russia's president.
"Litvinenko didn't die from stomach pain - he was killed because of everything he knew"Mario Scaramella, one of the last to meet Litvinenko
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Al Jazeera's correspondent in London reports that family members of Litvinenko do no want discussion but action.
British paper The Guardian published on Saturday what it said were extracts from the emails.
"All SVR [Russian foreign intelligence service] officers are sure that PG [journalist Paolo Guzzanti] and MS [Scaramella] still live closely with 'enemy No 1 of Russia' – [self-exiled oligarch] Boris Berezovsky and his 'companion-in-arms' - first of all A Litvinenko," one email read.
"Russian intelligence officers speak more and more about necessity to use force against PG and MS, considering their 'incessant anti-Russian activities' - as well as against Berezovsky and Litvinenko," the email continued.
Putin himself has condemned what he said was the use of Litvinenko's death for political purposes.
The Mitrokhin commission, an Italian commission of inquiry into KGB spy recruitment, was headed by Guzzanti and a senator from the conservative party of former prime minister Silvio Berlusconi.
In an interview with the Italian daily La Stampa, Guzzanti said: "I have no doubt that the current Russian secret services ... are behind this murder and not only this one."
Guzzanti alleged that Litvinenko was their third victim.
"The first was general Anatoly Trofimov, former deputy chief of the FSB, who was killed in front of his house in 2005 because he was Litvinenko's superior," Guzzanti said.
"The second was [journalist] Anna Politkovskaya, who had strong ties to Alexander [Litvinenko] and who had denounced the involvement of Putin's secret services in the war in Chechnya."
Politkovskaya, who exposed alleged abuses by Russian forces in Chechnya, was gunned down in an apparent contract killing at her apartment building in Moscow last month.