"With Pirelli, we can't brake hard enough .. and the traction has deteriorated," the Ferrari driver told the Spanish daily El Pais published on Monday.
"Previously when I reached the end of the straight I braked as hard as I could. If I do that now, they (the tyres) block, especially the back ones," the Spaniard said.
Italian manufacturer Pirelli takes over from Japan's Bridgestone as the new and exclusive supplier of tyres for the 2011 Formula One season, which begins with the Australian Grand Prix in Melbourne on March 27.
World champion Sebastian Vettel has also been far from impressed with Pirelli.
"The problem is the tyres wear down too fast," the German Red Bull driver told German television channel ServusTV recently.
"They are only good for 16 or 17 laps, then they start to break up and are ruined, then the driver doesn't have a chance.
"The feeling when driving is different and that is a pity for us."
Alonso unhappy with Pirelli tyres
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