Barack Obama has ordered Republican party activists to leave his wife alone after a foretaste of the rough ride to come if he wins the Democratic presidential nomination.

The Democrat senator for Illinois sent out the blunt message: "Lay off my wife" after the Tennessee Republican party released a four minute video on YouTube, rehashing comments that Michelle Obama made during campaigning in Wisconsin in February.

The comment on which the video focuses is Mrs Obama's statement: "For the first time in my adult life, I am really proud of my country," a remark which several commentators attacked as unpatriotic.

The sentence is replayed six times in the video, interspersed with commentary by Tennesseans on why they are proud of America. In a news release that included a link to the video, Tennessee's GOP said "the Tennessee Republican Party has always been proud of America." It urged radio stations to play "patriotic music" during Michelle Obama's visit to Nashville last Thursday.

Today Mr Obama gave notice that he was angered by the strategy, describing the strategy as "low class." When he was asked in an interview this morning on ABC's "Good Morning America" about the video, he stressed that any negative campaigning should be directed only against himself.

"The GOP, should I be the nominee, can say whatever they want to say about me, my track record," Mr Obama said.

"If they think that they're going to try to make Michelle an issue in this campaign, they should be careful because that I find unacceptable, the notion that you start attacking my wife or my family.

"Whoever is in charge of the Tennessee GOP needs to think long and hard about the kind of campaign they want to run, and I think that's true for everybody, Democrat or Republican," Mr Obama said in the ABC interview, adding: "These folks should lay off my wife."

The tactic has similarities to the relentless campaign against John Kerry, the Democratic presidential candidate in 2004, whose proud Vietnam war record was repeatedly smeared by a lobby group calling itself the Swift Boat Veterans.

The smears played into the hands of Mr Kerry's Republican opponent, George Bush, who never served in Vietnam. The veterans' group was reported to have funding links with the Republican party.

Mrs Obama has clarified the remark in the light of the criticism it attracted, saying she had meant she was proud of how Americans were engaging in the political process and that she had always been proud of her country.

Today she joined her husband in the ABC interview, saying she believed voters were more focused on the issues than on smears.

“We are trusting that the American voters are ready to talk about the issues and not talking about things that have nothing to do with making people’s lives better,” she said.

Mr Obama said that his wife loved her country. "For them to try to distort or to play snippets of her remarks in ways that are unflattering to her is, I think, just low class. I think that most of the American people would think that as well."

Tennessee's Republican Party was roundly criticised in March, including by John McCain, the Republican candidate, for a news release that used Mr Obama's middle name — Hussein — and showed a photo of him wearing what it said was "Muslim attire."

The release was eventually removed from the party's website at the urging of the state's two Republican senators and Mike Duncan, the Republican National Committee Chairman, who said he "rejects these kinds of campaign tactics."

Times Recommends

• It’s only Brits who don’t appreciate me, says Blair
• Party’s over for Greek graspers
• White House tightens security for Xmas marathon