Italy is reeling from revelations from a former boss that the mafia made money from the late 1980s onwards by dumping huge quantities of toxic waste throughout southern Italy, endangering the lives of millions of people.

Carmine Schiavone, an ex-affiliate of the Camorra, the Neapolitan branch of the Italian mafia, made the shocking statement to a parliamentary committee of inquiry in 1997. His remarks were protected by state secrecy laws until they were lifted on Thursday.

“I know from experience that until 1992 (the year he was arrested), southern regions… were all contaminated by toxic waste from all over Europe, not just Italy,” Schiavone told lawmakers.

“We are talking millions, not thousands” of tons of toxic material, he said.

There was industrial waste from northern Italy, but also radioactive material from Germany, which was disposed of in caves up to 50m deep, near groundwater reserves, as well as in fish tanks and lakes, Schiavone said.

The Camorra is continuing its activities today, he said on Friday, after a transcript of his 16-year-old statement was made public. “They did it then and they are still doing it,” he told RAI state television.

In Parliament, Schiavone explained how the Casalesi, a powerful Camorra clan he belonged to, controlled the waste disposal business between Latina, 70km south of Rome, and Caserta, 40km north of Naples.

Residents of Casal di Principe, the town the Casalesi have taken their name from, and of surrounding areas, “risk all dying from cancer within 20 years… indeed, I don’t believe they will survive”, Schiavone said.

There are no overall statistics on the rise of cancer rates in Naples and its surroundings, but in May it was revealed that a local government health unit in the city had found that cases in its ward had increased from 136 in 2008 to 420 in 2012.

Father Maurizio Patriciello, a local priest who is involved in grassroots protests against waste pollution, was outraged by Italian authorities’ failure to alert local residents about the dangers revealed by the mafioso.

“If sixteen years ago the state had warned us citizens of Naples and Caserta that we would have died of cancer from dumped waste, at least those who were younger could have packed their bags and gone living elsewhere,” he told Italy’s Huffington Post on Saturday.

Allegations about toxic waste have circulated for years. Roberto Saviano, an anti-Mafia author, wrote about the Camorra’s deadly business in his 2006 bestseller Gomorrah, which was later turned into a critically acclaimed film.

“The open secret has been revealed,” Legambiente, Italy’s biggest environmental association, said after the publication of the Schiavone testimony.

It called for “the truth” on “who, in politics, kept quiet for so many years and failed to act… pretending not to know, amid general indifference, and becoming a de facto accomplice of the massacre in those lands”.

Before the parliamentary committee, Schiavone said that in the late 1980s and early 1990s the Camorra directly appointed mayors “in all 106 municipalities of the province of Caserta”.

He said it could also count on the tacit support of national politicians such as former ministers Francesco De Lorenzo, Vincenzo Scotti, Antonio Gava, and former premier Ciriaco De Mita, currently a member of the European Parliament.

“It is not like they were clan members, or mafiosi; unfortunately each one of us has only one vote, and to win a lot of them, especially in certain areas, you need a lot of friends,” Schiavone said.

The former mobster was a key witness in a trial that ended three years ago when life sentences against 16 Camorra bosses – including his cousin Francesco – were upheld by Italy’s highest appeals court. The legal case lasted almost 12 years.

In a BBC interview published on Thursday, Schiavone said he testified against his former accomplices, becoming a mafia turncoat, because he felt guilty about the pollution.

“I did it when I knew that people were doomed to die from cancer. They had injected all this land – millions of cubic metres – with toxic substances. A scary cocktail,” he said.

“Even relatives of Camorristi are falling ill from cancer. How stupid,” Father Patriciello, the local priest, said. He plans to take part in a popular protest due to take place in Naples on November 16.

Meanwhile, authorities have pledged clean-up action. On November 6, experts were due to begin checking the coastline in Licola, just north of Naples.

“Those who have polluted Campania (the region around Naples) will have to pay,” said Agriculture Minister Nunzia De Girolamo.