Last year's tournament brought in 220,000 spectators, but organisers were hoping to deal with coronavirus regulations by restricting numbers at this year's event, which begins on Monday, to 6,000 per day in four separate zones.
“It is a huge injustice,” said FIT president Angelo Binaghi during a press conference in Rome.
“While other sports, in other (Italian) regions, have been authorised to accommodate thousands of people, no one will be able to enter the biggest sporting event in our country.”
The Italian government has given the go-ahead to small numbers of fans at several other events, notably Formula One's Tuscany Grand Prix in Mugello and the MotoGP meeting in San Marino, both of which take place next weekend.
But bigger events will continue to be played behind closed doors as the current coronavirus restrictions were kept in place under a new emergency decree on Monday.
Binaghi said health authorities had rejected their suggested protocols, and were not swayed by the French Tennis Federation allowing 11,500 per day for the French Open in Paris later in the month.
Binaghi also launched a swipe at the regional authorities in Lazio, where the Masters is taking place, for not getting behind the event, claiming they “did not want to take responsibility” for green-lighting public admission.
“The damage is enormous,” he said. “If we had known before, we would have organised the tournament in another region, in Genoa for example, or in Puglia.”
The Italian government also resisted growing demands from football clubs, with Serie A set to restart on September 19th.