Spam accounts for close to half of all text messages sent to cell phones, a percentage that has more than doubled in just one year, said a text messaging provider Monday.

According to Wireless Services, which claims to manage 15 to 20 percent of all text message traffic for U.S. wireless carriers, 43 percent of all text is now spam. A year ago, said Wireless Services, that rate was just 18 percent.

In December 2004 alone, added the Bellevue, Wash.-based firm, 1.2 million spam text messages were blocked by the company.

Wireless Services attributes the surge to smarter and more sophisticated spammers who are moving beyond the traditional venue of e-mail. "While they initially sent messages to mobile phones via the Internet, they are now savvy enough about wireless networks to foil anti-spam technologies developed with e-mail in mind," said Rich Begert, the chief executive of Wireless Services, in a statement.

The economics of cell phones -- and thus the spam they receive -- is quite different from e-mail, Begert noted.

"With mobile spam, consumers have to pay for the delivery of annoying, unwanted messages to their personal phone," he said as he made a pitch for his company's services.

"Unless carriers get in front of the issue, they could see increased churn, unwanted legislation, and certainly, a rise in customer service calls," Begert said.