Italian ministers, prosecutors and police chiefs have denounced a European court ruling that tough prison regimes for mafia bosses violate their human rights, warning the judgment will hinder the fight against organised crime across the continent.

On Tuesday, the Strasbourg-based European court of human rights (ECHR) ruled Italy should reform its justice laws that state mafia inmates cannot have time off life sentences unless they cooperate with investigations.

The ruling focused specifically on the case of Marcello Viola, who was sentenced in 1999 to life imprisonment for mafia association, multiple murder and robbery. In its ruling, the European court urged Italy to revise its laws mandating life sentences for very serious crimes and ruling out sentence reductions unless inmates turn informant.

The ECHR ruling does not mean it is recommending Viola’s release. But the judgment stated that life terms subjected prisoners to inhuman and degrading treatment, violating their dignity.

Profile Three high-profile mafia prisoners Show Giovanni Brusca The 62-year-old, nicknamed "The Swine" and "The People Slayer", set off the explosive that killed the anti-mafia prosecutor Giovanni Falcone in 1992. He also led the team that kidnapped the son of an informant in 1993, and gave the final order for the boy to be strangled in 1996 after years of torture. He was jailed the same year. Pasquale Condello Known as the "The Supreme One", the 69-year-old was the most feared and respected leader of the 'Ndrangheta, the Calabrian mafia. According to a mobster who turned state witness, Condello participated in the killing of an older 'Ndrangheta boss in 1975. He was arrested in 2008 having been on the run since 1987. Giuseppe Setola The 48-year-old, a former boss of the Casalesi clan from Caserta, has been convicted of ordering or carrying out 18 murders in 2008, including the drive-by shootings of six west African immigrants. He was arrested in 2009 after a huge manhunt. Photograph: Alessandro Fucarini

The ruling has triggered an outcry among investigators, who claim it does not take into account the context and history of the mafia in Italy.

“The ruling by ECHR cancels 150 years of struggles against the mafia,’’ said the chief prosecutor of Catanzaro, Nicola Gratteri, one of Italy’s most respected anti-mafia prosecutors. “The judges’ decision risks having serious repercussions, not only for our country but for the whole of Europe.”

Italy toughened jail conditions for mobsters and terrorists in the wake of bloody feuds in the 1980s and 1990s, which culminated in the murder of two top Sicilian anti-mafia magistrates, Paolo Borsellino and Giovanni Falcone, in 1992. Article 41-bis, of the Prison Administration Act, allows the authorities to suspend certain prison regulations for mafia boses, with the aim of cutting inmates off completely from their criminal associates. The new regime banned the use of telephones, any association or correspondence with other prisoners, or meetings with third parties.

According to prosecutors, the fear of unrelenting prison conditions is key to persuading mafiosi to become informers. In order to avoid living a completely isolated life in jail, many mobsters have turned state witnesses, contributing to further arrests and the weakening of Cosa Nostra.

“In few words, only jail scares the mobsters,” the anti-mafia magistrate Nino Di Matteo told the newspaper Il Fatto Quotidiano.

“Life sentences and 41-bis are two crucial weapons in the fight against the mafia,’’ said Gratteri. “If these weapons against organised crime change, the whole fight against the mafia collapses. What these Strasbourg judges do not understand is that a mafia boss remains a lifelong boss. Even if he has been detained for decades, even if he is old and sick, even if he is paralysed in a wheelchair, he continues to command and to give orders by moving his eyes. If we delete these laws, we give the mafia bosses the hope of returning to command even in 10 or 15 years.”

Students of the Istituto Nautico Gioeni-Trabia, in Palermo, Italy, in front of a mural of the judges Giovanni Falcone and Paolo Borsellino, killed by the mafia. Photograph: Alessio Mamo/The Observer

The Strasbourg court’s ruling will not determine a change in Italian law, but prosecutors fear it will trigger an increase in petitions by mafiosi asking for their benefits or their release.

The battle to toughen prison regimes has a long and violent history. From May to August 1993, five car bomb attacks in Rome, Florence and Milan killed 10 people and injured dozens in a coordinated attack by the Sicilian mafia in response to the 41-bis regime. The attack was ordered by the Corleonesi mafia clan, led by Totò Riina, one of the most ruthless criminals in the history of Cosa Nostra. Riina had been arrested a few months before the bombings in January 1993 and was sentenced to life imprisonment under the 41-bis prison regime.

Along with many of his clan members, Riina refused to collaborate with the prosecutors and died in prison in November 2017.

“I understand the reasons for the Strasbourg court ruling but we must also take reality into account,” Sergio Lari, a former anti-mafia prosecutor, told the Guardian. For more than 10 years Lari was the head of the Palermo anti-mafia directorate and the lead investigator in the Falcone and Borsellino killings. “Cosa Nostra launched a real war in Italy that caused the death of innocent people, including children, magistrates and journalists. It was a war that no western country had ever faced since second world war. How can you ignore this historical fact?”

The ruling has also been criticised by some members of the Italian government. Luigi Di Maio, the foreign minister and the leader of the ruling Five Star Movement, wrote on Facebook: “The history of our country has left us too much blood and pain. We will not look the other way.”