A number of public interest groups have filed a letter with the Federal Communications Commission requesting the agency investigate claims that new plans being offered by mobile provider MetroPCS block Internet content, applications and websites.

The public interest groups who sent the letter to the FCC include Free Press, the Center for Media Justice, Media Access Project, New America Foundation Open Technology Institute and Presente.org .

Last week, MetroPCS, the nation’s fifth-largest wireless provider, announced a new plan under which MetroPCS — not its customers — will decide which Internet sites and services are important. MetroPCS is advertising unlimited talk, text, “Web browsing” and YouTube at a base price of $40 per month — with all other uses only available on higher tiers at a higher cost.

The plans would effectively create a “walled garden” that excludes Skype, Netflix and other popular consumer Internet services, putting those service providers at a competitive disadvantage and restricting consumer choice and innovation.

“MetroPCS’s practices are particularly problematic because, as the company itself recognizes, it disproportionately serves lower-income subscribers, the same audience that is increasingly relying on mobile access to the Web, said Chris Riley, Free Press counsel.

“A walled garden in mobile broadband leaves a large number of Internet users on the wrong side of the digital divide.”