The episode is part of a long-running saga that reads like an international spy story, with roles for politicians, secret services and organised crime, and punctuated by violent deaths.

The find, just over a week ago, stemmed from information provided by a former member of the Calabrian mafia – also known as the ’Ndrangheta – who told investigators he blew a hole in the hull of the vessel, which sank 20 miles off the Calabrian coast near the town of Cetraro. Francesco Fonti told investigators the ship was carrying radioactive waste from Norway and was one of three vessels he had sunk on the orders of the ’Ndrangheta.

A murky video recorded by a remote-controlled submersible shows the vessel lying on the seabed and at least one barrel that had spilled from its damaged hull. The find lends new weight to Fonti’s astonishing tale, which he first shared with investigators in 1992 and which implicates senior members of Italy’s political establishment.

“It was an easy and habitual procedure … there are around 30 ships lying off the coast of Calabria,” Fonti told news magazine L’Espresso. “I sank three of them.”

Fonti claimed that Christian Democrat politicians, including former prime minister Ciriaco De Mita, had commissioned some of the illegal disposal operations, sometimes using the secret services to screen out their involvement. Other toxic waste had been exported to Somalia, Fonti said, with Socialist politicians Gianni De Michelis and Bettino Craxi intervening to ensure that Italian peacekeeping troops turned a blind eye to the deliveries.

“I only describe episodes where I was one of the protagonists and I am waiting for someone to demonstrate I am wrong,” Fonti told L’Espresso.

De Mita has denied the claims and threatened legal action.

Fonti has accused other countries of involvement in the illegal trade, including Russia, Germany and the United States. He told L’Espresso he had helped dispose of toxic aluminium waste for the Russian businessman Oleg Kovalyov, “who was close to the then KGB agent Vladimir Putin”.

The Cetraro find – believed to be a missing ship named Cunsky – also vindicates the work of Mario Scaramella, the self-styled environmental expert who worked as a consultant for magistrates in Reggio Calabria and claims to have identified the wrecks of 20 missing vessels. Scaramella is better known as the man once suspected of poisoning the former Russian spy Alexander Litvinenko.

Investigating the fate of the hazardous waste has been a risky business too. A key investigator, ship’s captain Natale De Grazia, died of a heart attack – aged just 39 – while on his way to the port of La Spezia to interview witnesses.

And the murder in Somalia of TV journalist Ilaria Alpi and her cameraman, Miran Hrovatin, has been attributed to their interest in the troubled east African country as a convenient dump for Italian toxic waste.

A parliamentary inquiry concluded that the two journalists were shot dead by bandits in 1994 in a botched kidnap attempt. But two years ago a judge ordered Rome prosecutors to continue their investigation, saying a murder on commission intended to prevent information reaching the Italian public about “a traffic in arms and toxic waste between Italy and Somalia” was the most likely explanation.

A copy of Ilaria Alpi’s death certificate was found at the home of controversial naval engineer Giorgio Comerio, who was allegedly involved in negotiating with Somali authorities for permission to dump hazardous refuse.

Comerio was the founder of a Swiss company called ODM (Oceanic Disposal Management), which pioneered research into the possibility of loading toxic waste onto torpedoes and firing them into the seabed. ODM reportedly explored a plan to bury Ukrainian asbestos in the Black Sea and dispose of hazardous waste from North Korea and Taiwan.

“What was missing until now was proof of the crime and the names of the alleged instigators,” said Antonio Pergolizzi, a spokesman for environmental group Legambiente. “This could give rise to a number of trials that could go on for many years.”

Pergolizzi said the powerful interests involved could help to explain why previous investigations had run into the sand: “It’s a very complex affair that brings to light a piece of rotten politics … I doubt we will ever discover who the top people really were.”

Fonti told L’Espresso: “I still find myself in an absurd situation. I live in hiding, without protection, with the danger members of the clan I used to belong to could be looking for me, as well as sectors of the state that used me and other ’Ndranghetisti as their footsoldiers.”