Netflix has been sued by the National Association of the Deaf for failing to offer closed-captioning on enough of its streaming content.

In a lawsuit (PDF) filed Thursday in U.S. District Court for the district of Massachusetts, the NAD alleges that Netflix is in violation of the Americans with Disabilities Act by not providing captions for most of its "Watch Instantly" streamed movies and TV shows.

Pointing to the approximately 36 million Americans who are deaf or hard of hearing, the National Association of the Deaf says that it and members of the deaf community have already raised the issue with Netflix via letters, blogs, and petitions, urging the site to provide equal access to its streaming content. Despite these complaints and requests, the group says that Netflix has so far set up captions on only a small number of the overall titles on its "Watch Instantly" service.

The ADA requires that all "places of entertainment" provide "full and equal enjoyment" for people with disabilities, according to the NAD, which is asking the court to declare Netflix in violation of the act and order the company to provide captions on all streaming content.

"We have tried for years to persuade Netflix to do the right thing and provide equal access to all content across all platforms," NAD President Bobbie Beth Scoggins said in a statement. "They chose not to serve our community on an equal basis; we must have equal access to the biggest provider of streamed entertainment. As Netflix itself acknowledges, streamed video is the future and we must not be left out."

When asked by CNET to comment on the matter, a spokesman for Netflix said that the company's doesn't comment on lawsuits.

But in a blog posted in February, Neil Hunt, the company's chief product officer, said that 30 percent of the streaming content has subtitles and he expects to increase that amount to 80 percent by the end of this year. In a blog from 2009, Hunt cited technical challenges that were stalling the delivery of subtitles to Netflix's streaming content.

The NAD lawsuit claims that the "process of captioning is both "technically possible and relatively simple to achieve."

Updated at 3:25 pm PT with response from Netflix.