A ticket normally costs €18 (US$20) but the official website on Tuesday (Jul 18) showed there were just three places left until Aug 7. By contrast, websites of local guide companies were offering numerous tours ranging from €37.50 to €74.00 euros.
There was no immediate comment from CoopCulture or the guide companies.
Carlo Rienzi, the head of consumers rights body Codacons, said “secondary ticketing” was costing Italy millions of euros.
“We ask the government to introduce new provisions capable not only of blocking secondary ticketing, but also of imposing very heavy penalties on those sites,” Rienzi said in a statement.
Built 2,000 years ago, the Colosseum was the biggest amphitheatre in the Roman empire and was used to host gladiator fights, executions and animal hunts.
It has recently grabbed media attention as visitors have been caught scribbling graffiti on its walls.