The Spanish giants were forced to dismiss reports from various local media outlets that the £85m star's latest injury was a result of a slipped disc.
The Wales international's fitness has recently been criticised by the Spanish media, with some claiming that the 24-year-old winger could be sidelined for months.
"Certain media outlets surpass what criticism is," Perez told Punto Pelota. "It's a permanent campaign. The information published about Bale is extremely cruel, even if it was true.
"Being false, it becomes clear that they have a target. Should Bale have a slipped disc, we would have told the media so. We would never have signed him if that was the case.
"Here in Madrid, you know the press try not to appear as Madridistas. News like the report about Bale would never have been published in Barcelona, being false as it is. There's a campaign against myself and others at Madrid."
Bale has made just three appearances for the club since arriving from Tottenham Hotspur in August.