Eight consumer and public-interest groups filed a complaint with the U.S. Federal Communications Commission, saying mobile phone providers should not be able to block text messages from political groups and advertisers.

The petition, from Public Knowledge, the Consumer Federation of America, Consumers Union, and other groups, comes after Verizon Wireless decided in September to block text messages on its network from abortion rights group Naral Pro-Choice America, then reversed that decision the same day it was reported in the media.

"Mobile carriers currently can and do arbitrarily decide what customers to serve and which speech to allow on text messages, refusing to serve those that they find controversial or that compete with the mobile carriers’ services," says the petition, filed Tuesday. "This type of discrimination would be unthinkable and illegal in the world of voice communications, and it should be so in the world of text messaging as well."

Verizon Wireless and other carriers have also blocked VoIP (voice over Internet Protocol) provider Rebtel from advertising its inexpensive mobile voice calls on their networks, the petition notes. Carriers "publicly admitted that they denied Rebtel's request because Rebtel's services competed with their own," the petition says. "The wireless industry should not be permitted to make these discriminatory decisions."

But Jeffrey Nelson, a Verizon Wireless spokesman, said carriers should be under no obligation to carry advertising from competitors. While Verizon Wireless called the blocking of Naral's text-messaging campaign a mistake and an "isolated incident," the decision to deny Rebtel access to the Verizon mobile network was intentional, Nelson said

Nelson compared Verizon's decision on Rebtel to a newspaper not accepting advertising from another newspaper. "We're not blocking anything," he said. "We're not allowing them to advertise."

If the FCC grants the petition, it would open up mobile phone networks to millions of pieces of text spam, Nelson added. Each month, Verizon Wireless currently blocks between 100 million and 200 million unwanted text messages advertising pornography and other products, he said. Text messaging in the U.S. would quickly become "unusable" because of all the unblocked spam, Nelson said.

"I don't think [the consumer groups] understand what would happen if they're successful," he said. "If the folks who filed with the FCC get their way, it'd be a free-for-all."

Hugh McCartney, CEO of spam-filtering vendor Cloudmark, said a blanket prohibition against text-message blocking could cause major problems. In parts of southeastern Asia, mobile phone subscribers are already getting 20 or more spam text messages a day, he said. Even regulations that prohibit carriers from blocking text messages from political or nonprofit groups could open subscribers up to spam, he said.

"Spammers are smart enough," he said. "They will put down nonprofits as being the providers."

The consumer groups said that text blocking is evidence of a need for net neutrality rules, which would prohibit network providers from blocking or slowing content from competitors.

"For many people, texting has replaced calling as a way of keeping in touch," Gigi Sohn, president of Public Knowledge, said in a statement. "We need to have the FCC set the rules for the entire industry, and for a generation of people that depends on texting. There is no place for discrimination in text messaging."