The mafia are the biggest threat to southern Italy's economic prospects, Prime Minister Romano Prodi has told a conference against organised crime.
Naples has been gripped by a series of mafia-related killings
"Lawlessness is the greatest obstacle to economic growth in southern Italy," he told the three-day forum in Rome.
Mr Prodi was briefly heckled by an audience member who said parliament must first purge itself of corrupt MPs.
Some 2,500 people have died in violence blamed on Italy's three main mafia groups in the last 10 years.
According to the organisers of the anti-mafia forum in Rome, politicians have failed to tackle the problem.
Top politicians, senior judges, police and security officials and civil society groups were expected to be among the 2,500 participants at the conference.
An escalating turf war between mafia gangs in the Italian city of Naples has led to recent calls for the army to be deployed.
"No-one talks about the mafia except in emergencies, as in Naples recently," Lorenzo Frigerio of the anti-mafia group Libera told the AFP news agency.
"You forget that it is a permanent presence in the country and that it has not missed the train of globalisation," Mr Frigerio said.
He added that the issue had been hardly mentioned during the election campaign earlier this year.
Mr Prodi told the forum: "Arresting the mafia chiefs is not enough, we must strike the organizations at their heart."
"More than once I've had to throw up my hands with foreign businessmen, who have refused to invest in the south because there weren't enough guarantees," he said.
More police have recently been deployed in Naples
As Mr Prodi described his government's plans to combat the mafia, he was interrupted by an audience member, who said: "You could begin by throwing out of parliament MPs found guilty of corruption."
Last week, Italian police carried out a series of co-ordinated raids across the country, detaining more than 100 alleged mafia members suspected of drug-trafficking.
In a separate development, a Sicilian judge on Wednesday sentenced dozens of associates of jailed mafia boss Bernardo Provenzano for a total of 300 years, Italy's Ansa news agency reported.
According to the BBC's David Willey, the Sicilian mafia remains hugely potent as it expands from its traditional drug trafficking to people smuggling and siphoning off millions of dollars from public works contracts.