They said the imams were free to enter and travel within the prisons at will, spreading messages and propaganda and leading to the creation of jihadi cells behind bars.
They also said the 70 mosques within the country’s jails were leading to a spike in jihadi recruitment.
Donato Capece, the general secretary for Italy’s biggest prison guard union, said prisons needed help to stop the growth of extremism.
He said: “There are twenty imams coming in and out [of the country’s jails] just like parish priests do. And that is in addition to 150 self-proclaimed imams, who are in jail serving a sentence.
“They are all free to move from section to section from the morning until the evening and this has caused the elimination of the guard who went to check each section from time to time.”
He said there was enough evidence to show extremism in prisons was growing to demand more help from the government.
Mr Capece said: “Let’s remember the last arrest in Ciampino of an alleged terrorist who had been radicalised in prison but there are several precedents.”
He said prisoners were losing their discipline and attacking guards or starting fights leading to an environment of chaos in which terrorist recruiters flourish.
Mr Capece said: “They have fun kicking men in uniforms or triggering riots. This is the way used by suspected terrorists to contact ordinary people, who are indoctrinated and become a risk for the future.”
He concluded by appealing for support from the Italian government when it comes to hiring new guards – especially those who speak Arabic.
Mr Capece said: “We must remember that many of these men speak Arabic and Arabic is not only a national language but consists of many dialects that we do not know. If we want to do prevention, we must at least understand them: hiring people who know the language or do ad hoc training to allow staff to understand and do prevention. Then there is also the problem of government cuts.
“We went from 45,000 [staff members] in 2001, provided by the law, to the present 38,000. To this, we can add the fact that so many old agents are retiring.”