The town hall of San Sebastián de los Reyes in Madrid's north is looking for a solution after two organizations representing homosexuals and transsexuals lodged official complaints against the barring of their sites.
Madrid's Cogam and the national FELTGB association both say users of the municipality's public Wi-Fi network can't access their sites.
The network also blocks users from searching for terms such as "gay", "lesbian", "transsexual" and "bisexual", according to Spanish newspaper 20 minutos.
Staff at the council said sites containing "adult information" were blocked because the network was open to everyone, including children.
But a council spokesperson said the problem lay with the multinational company that set up the network.
"This company categorizes pages which could be harmful like this connected with online gaming, pornography or violence," the official explained.
"(Sites like) Cogam and FELTGB could have been blocked because (they contained) similar terms, but not because of a decision we made," he added.
"We are not a porn site!" Cogam President told Ronny de la Cruz told 20 minutos. "We are registered as providing information of public interest."
Cogam have now sent a letter to the San Sebastián de los Reyes asking them to provide information on steps they are taking to remedy the situation.