* NAB appeals FCC rules to post political ad buys online
* Says rules overstep FCC's authority, inhibit free speech
* FCC defends rules as common-sense update
* Rules still on track to reflect 2012 political spending
WASHINGTON, May 22 (Reuters) - The National Association of Broadcasters has asked a federal appeals court to block new rules that would force broadcasters to reveal online who is paying for political campaign ads and just how much they are shelling out.
The Federal Communications Commission adopted the rules last month in an effort to provide insight on campaign spending ahead of November's congressional and presidential elections.
NAB filed a petition for review on Monday with the U.S. Federal Court of Appeals for the District of Columbia Circuit, charging that the rules are arbitrary, capricious, violate free speech protections in the U.S. Constitution and go beyond the FCC's statutory authority.
The trade group said the requirement to publish political advertising contracts and the rates stations charge online would "directly and adversely impact NAB and the broadcasters whose interests it represents."
During the FCC's rulemaking process, NAB had cited the "fundamental unfairness" of leaving their cable and Internet competitors unaffected by the new rules.
Broadcasters unsuccessfully tried to get the then three-member FCC to support a compromise proposal that would have allowed them to leave out specific ad rate data but disclose the aggregate amount of political spending by buyers.
Republican Commissioner Robert McDowell sympathized with the broadcasters' arguments that the FCC order would unfairly expose their advertising rates to rivals, but his dissent to portions of the order was not enough to keep the rules at bay.
TV stations have been making public their records of campaign advertising buys and other community-related issues since 1938 as part of their public interest obligation.
"The public file rules are a common-sense update by the FCC to move from paper to online access to public information in the digital age," an FCC spokesman said on Tuesday.
"The rules are consistent with Congress's directive to ensure public availability while providing cost-savings for broadcasters," he added.
The new data format, to come initially from the four biggest TV broadcasters in the top 50 media markets, includes detailed information on who paid for political ads, key personnel of the groups buying ads, when political ads aired and rejections of requests to buy air time.
The four biggest broadcasters are ABC, operated by Disney Co , CBS Corp, News Corp's Fox, and NBC, controlled by Comcast Corp.
The top broadcasters would have to upload their political files to a database hosted on the FCC's website, beginning 30 days after the rules receive approval from the Office of Management and Budget.
The FCC expected the rules to swiftly gain OMB approval, in time to reflect spending during the 2012 campaign cycle.
The litigation is unlikely to hamper that intent, said Corie Wright, an attorney for the public interest group Free Press. The broadcasters did not seek an emergency stay of the rules in their petition.
The new rules would come at a time when political spending has hit record highs. Independent "super" political action committees have already spent nearly $126 million this campaign cycle compared with only $32.7 million spent in the same time period during the 2008 election.
These "Super PACs" can raise and spend unlimited amounts to help politicians, as long as they do not coordinate with official campaigns.