BMW Sauber driver Nick Heidfeld says Formula 1's tires could be "ten times better" if there was more than one supplier in the sport.
Bridgestone currently supplies the whole field after the FIA introduced a control-tire rule from the 2008 season.
Although the Japanese company has taken two different compounds to each grand prix this season, there has been tire issues in several races, as drivers are forced to use both types during races.
Heidfeld reckons the regulation creates "artificial" racing, and he feels the tires could be much better.
"For me, on the long runs, they lasted OK but for some other guys they went away a lot quicker," Heidfeld said in Singapore. "We have the prime tire which is possible to do the race, obviously better, it maybe doesn't help things but the tire is not too soft.
"As there is no competition, they could be ten times better, we could have tires that are softer, offer more grip and last the distance. On top of that, the idea of having to use both compounds is artificial to create something that is not sport."
He added: "There is no tire testing, we have the same tires for the whole year. What is really surprising is that even now so late in the season sometimes things happen that you didn't expect. It's not just for the team, it's for the whole paddock."