Frontier Communications has admitted in a December regulatory filing it lost a combined 60 percent of its residential and business landline customers in Washington over the last decade, with more than 15,000 more departing during the first nine months of 2012.

The company revealed those numbers as part of an effort to win “minimal regulation” in the state of Washington, claiming its cable, wireless, and Voice Over IP competitors have eaten away its customer base. During the period between 2000 and 2011, the number of access lines served by Frontier in Washington declined from 895,435 to 342,869.

Frontier revealed it lost 15,310 more customers from March-September 2012 in cities like Everett (1,302), Marysville (2,009), and Redmond (2,975). Many of those customers took their business to Comcast. Others rely on wireless service Frontier does not provide.

Frontier claims it faces robust competition in Washington and should be entitled to deregulation.

“These alternative providers have captured a significant share of the market for business and residential telecommunications services and additional features,” Frontier’s filing says. “Frontier is no longer the largest or predominant provider of telecommunications service.”

In Washington, companies like Frontier now just hold 19% of the voice telephone business. Wireless providers are now the predominant voice service provider, serving 6.1 million subscribers in Washington.

Frontier admits the competition has been beating the company’s pants off:

“The alternative service providers have clearly been successful in competing with Frontier as evidenced by the persistent and continuing loss of access lines by Frontier,” Frontier’s filing says. “As noted above, Frontier has experienced a 62% reduction in the number of access lines it serves in Washington from 895,435 as of January 1, 2001 to 342,869 as of September 30, 2012. This loss of access lines has been ubiquitous across Frontier’s exchanges in that all but one of Frontier’s 102 exchanges has experienced line losses since 2009.”

Deregulation would allow Frontier to increase prices or change how its markets and bundles certain products. It would also reduce the amount of oversight the company faces from state regulators.

The Washington Utilities and Transportation Commission temporarily set aside Frontier’s request at a meeting held Jan. 31. The regulator wants further time to investigate Frontier’s petition and will schedule future hearings on the matter in the future.

Thanks to Stop the Cap! reader Steve who first noticed the regulatory filing.