Caterham's Vitaly Petrov has voiced his unhappiness with the Mugello circuit, saying the track is "dangerous" and not up to standard.
After a four-year absence, in-season testing returned to F1 this season and teams agreed to stage the three-day session at the Italian track.
Several drivers praised the high-speed circuit after the first two days of testing while the track's director Paolo Poli suggested they could look to make a return to the F1 calendar in the near future if they continue to develop the venue.
However, according to Petrov they are still a long way away from being up to standard.
"Some drivers don't think it is good that we are testing here and I have to agree," the Russian told Germany's Autobild.
"It is a very dangerous track that does not offer a lot of space in some places. The walls are very close to the track.
"Overall, the track is too narrow for my liking. Even a small problem with the car like a drop in tyre pressure can result in a major accident. "