New York-based cable television provider Cablevision has filed suit in federal court in Brooklyn against Verizon over claims made in the latter’s advertising about Cablevision’s internet connection speeds.

Verizon has been running a series of ads for its FiOS network. In these ads the company cites an FCC report that says that during peak hours Cablevision’s broadband customers were seeing download speeds that averaged 50% of the company’s advertised speed of 15 megabits per second (Mbps). Cablevision objects to Verizon’s use of the report in the ads, arguing that the information on Cablevision’s data speeds is outdated. Moreover, it argues that Verizon has continued to run the ads despite repeated contact between the two companies in which Cablevision has made Verizon aware of the inaccuracies.

The Measuring Broadband America report was released by the FCC in March and continued to be updated until June. Verizon ads are accurate in that the data in the report does show Cablevision customers experience less than 60% of promised download speeds during peak hours. The chart from the original report is below:

Cablevision’s argument, though, is that although the data was accurate at the time of the report, it is no longer so. The company argues that they have improved their broadband service dramatically since the report was released. What’s more, the FCC itself backs Cablevision up on this point. In a blog post dated Monday, Chief of the FCC’s Consumer and Governmental Affairs Bureau Joel Gurin discussed some of the positive changes that have already been brought about since the report’s release. He says that since the original report was released the FCC has continued to collect data on the broadband speeds. He singles out Cablevision as a particular example of the kind of improvement that has been observed since the report was originally published. He notes that in the most recent month for which the FCC has data, October, subscribers to Cablevision’s 15 Mbps broadband service were seeing sustained download speeds during peak hours of 90% of the advertised speed, as compared to an average of 89% among all the other non-Cablevision companies.

As of this afternoon, a page on Verizon’s website describing the company’s broadband performance still includes the following chart from the Measuring Broadband America report. Cablevision claims that Verizon has known the chart to be inaccurate for some time.

Verizon has said they will defend against the suit vigorously. Bloomberg is reporting a statement by a Verizon spokesman in which the company casts aspersions on the truth of Cablevision’s own advertising, and vowed to continue setting the record straight.