WASHINGTON—NBC asked GOP presidential candidate Mitt Romney on Saturday to pull a campaign advertisement made up almost entirely of a 1997 "Nightly News" report on Newt Gingrich's ethics committee reprimand.

The "History Lesson" ad started running in Florida on the weekend, when it is harder for stations to switch ad traffic even if they want to. Broadcast days before Tuesday's primary, the ad shows former NBC anchor Tom Brokaw saying that some of Gingrich's House colleagues had raised questions about the then-speaker's "future effectiveness."

Under Brokaw's image is a line that reads -- "Paid for by Romney for President, Approved by Mitt Romney."

The footage was used without permission and the extensive use of the broadcast "inaccurately suggests that NBC News and Mr. Brokaw have consented to the use of this material and agree with the political position espoused by the videos," NBC's vice president of media law, David N. Sternlicht, wrote Romney's campaign manager, Matt Rhoades.

"Aside from the obvious copyright issues, this use of the voice of Mr. Brokaw and the NBC News name exploits him and the journalistic credibility of NBC News," the letter said. The network asked for the campaign to stop running the ad immediately and revise any other videos or commercials to remove at NBC material.

"As a news organization, NBC News objects to any use of NBC News journalists and our copyrighted material that suggests to the public that we or our journalists are taking sides with any individual or organization involved in a political campaign or dispute, and we request that your organization respect that concern," the letter said.

Romney adviser Eric Fehrnstrom said the campaign isn't likely to stop running the ad.

"We just received the letter. We are reviewing it, but we believe it falls within fair use," he said. "We didn't take the entire broadcast; we just took the first 30 seconds."

NBC spokeswoman Lauren Kapp said a similar request went to other campaigns that "have inappropriately" used material from "Nightly News," "Meet the Press," "Today" and MSNBC. Kapp said she was not aware of such uses by other campaigns.

Brokaw said in a statement released by NBC that he was "extremely uncomfortable with the extended use of my personal image in this political ad. I do not want my role as a journalist compromised for political gain by any campaign."

Brokaw stepped down in 2004 after 21 years as anchor and managing editor of "Nightly News," but continues to report for the network, including on the 2012 presidential campaign.

Asked about Brokaw's concern, Fehrnstrom said only, "We respect him as a newsman who has a lot of credibility, but we believe this falls within fair use standards."

The House ethics panel investigated Gingrich's use of tax-exempt organizations. The case ended in January 1997 with a reprimand by the House and a $300,000 penalty against Gingrich for misleading the committee and prolonging its investigation.

Romney has sought the release of all records from the probe. The committee did make public its final report as well as exhibits -- which amounted to a comprehensive account of its findings. The head of the ethics committee during the Gingrich investigation, former Republican Rep. Nancy Johnson, said the committee traditionally does not publicly release investigative documents.

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