A telecom industry group Monday challenged "open Internet" regulations barring US broadband providers from separating online traffic into slow and fast lanes, hours after official publication of the order.

The US Federal Communications Commission published its "net neutrality" order in the federal register earlier Monday, making the hotly contested rules effective June 12.

USTelecom, a trade group that includes major broadband providers such as AT&T and Verizon, announced it had filed a lawsuit in federal court seeking to block implementation of the plan.

USTelecom president Walter McCormick said the FCC order is an "unjustifiable shift backward to common carrier regulation" and that the plan "slows innovation, chills investment, and leads to increased costs on consumers."

The FCC's 3-2 vote in February in favor of so-called "net neutrality" followed an intense debate in Washington pitting backers of online services like Netflix, Twitter and Yelp against big Internet service providers like AT&T and Verizon.

The ruling, on the heels of a long regulatory battle, sets a new standard that treats all Internet traffic as equal, preventing Internet firms from charging fees for better access.

Backers said the move guarantees Internet users can roam freely online and prevent any effort to stifle expression, but critics complained it would give the government too much control.

The new challenge means the case goes back to federal court just more than a year after an appellate panel struck down a similar order saying the FCC lacked jurisdiction to enforce net neutrality.

The FCC rewrote the rules, this time by reclassifying broadband as a "public utility" under a 1934 telecom law.

Backers of the new rule say it is needed to prevent big broadband firms from locking out new services which cannot or will not pay for "fast lane" service. But critics say it amounts to old-style regulation that lacks relevance in the digital era.

The trade group and a small Internet firm announced last month they were challenging the order but officials said courts would not hear the case until the official publication of the rules.