(CNN) - Hillary Clinton’s campaign is denying a Canadian report Thursday that suggests her campaign called representatives of that nation’s government to re-assure them that despite campaign rhetoric, they would not seek changes to NAFTA – an allegation they used against Barack Obama’s campaign in the days leading up to Tuesday’s critical primary votes.

"Unlike the Obama campaign, we can and do flatly deny this report and urge the Canadian government to reveal the name of anyone they think they heard from,” Clinton spokesman Phil Singer said in a statement.

Shortly before the Ohio primary, the Canadian network CTV broadcast a report that Obama economic adviser Austan Goolsbee had told officials with the Canadian consulate in Chicago that the campaign would not look to alter the trade agreement, even though the Illinois senator had pledged to do so.

That report became a lightning rod on the campaign trail in Ohio, where NAFTA is deeply unpopular.

The Canadian government has said it is investigating the source of the leak. The Canadian Press reported Thursday that the comment that sparked the original story may have come from Canadian prime minister Stephen Harper’s chief of staff, Ian Brodie – and that his remark had implicated Clinton’s campaign, not Obama’s.

The Thursday story also said CTV’s Washington bureau had initially decided to report on Clinton. The New York senator was mentioned in the final report, but it focused on Obama’s aide.

The Canadian Press said government officials did not deny the conversation took place, but that Brodie denied discussing either candidate.

Earlier this week, the Obama campaign admitted Goolsbee and consulate officials had spoken, but not under the direction of the campaign, and said that a leaked Canadian government memo implying otherwise had mischaracterized the substance of the discussion.

On Monday, the Canadian Embassy in Washington issued a statement on the controversy that “there was no intention to convey, in any way, that Senator Obama and his campaign team were taking a different position in public from views expressed in private, including about NAFTA.”

[cnn-photo-caption image= http://i.cdn.turner.com/cnn/2008/images/03/06/art.starr.gui.jpg caption="The Clinton campaign accused Obama Thursday of acting like Ken Starr."]
(CNN) - A Clinton campaign spokesman Thursday compared Barack Obama’s recent criticism of the New York senator to the actions of Whitewater prosecutor Ken Starr.

Since his losses on Tuesday night, Obama has stepped up his attacks on Clinton for her failure to release her most recent tax returns and other documents related to her time as first lady. Her campaign has said that she will release the tax records in advance of Pennsylvania’s April 22 primary, and that it cannot control the release of the White House schedules in question.

On a Thursday conference call with reporters, Clinton communications director Howard Wolfson said that the Illinois senator was attempting to sidestep questions about his readiness to lead the country. “He chose not to address those questions, but to attack Senator Clinton. I for one do not believe that imitating Ken Starr is the way to win a Democratic primary election for president," said Wolfson.

He also responded to Obama’s contention that Clinton had criticized Rick Lazio, her Republican Senate opponent in 2000, for not releasing his returns by noting that Clinton and her husband, former President Bill Clinton, had been making that information public for decades.

"As somebody who led the effort to ensure that Mr. Lazio provided his tax returns, certainly at that point he had not provided 20 years of his tax returns to the people of New York," Wolfson said.

Obama campaign spokesman Bill Burton responded to the criticism by accusing the Clinton team of a double standard.

“…We don’t believe that expecting candidates for the presidency to disclose their tax returns somehow constitutes Ken Starr-tactics, but the kind of transparency and accountability that Americans are looking for and that’s been missing in Washington for far too long,” said Burton, in a statement to reporters.

“And if Sen. Clinton doesn’t think that the Republicans will ask these very same questions, then she’s not as ready to go toe-to-toe with John McCain as she claims.”

- CNN Associate Political Editor Rebecca Sinderbrand

[cnn-photo-caption image= http://i.cdn.turner.com/cnn/2008/images/03/05/art.ticket.gi.jpg caption="Limbaugh said a ticket with Obama and Clinton doesn't have a prayer."](CNN) - Many Democrats have called the prospect of Hillary Clinton and Barack Obama teaming up for the general election a "dream ticket."

But conservative talk radio host Rush Limbaugh said Wednesday a presidential ticket that included a "woman and a black" doesn't "have a prayer."

"Let's say it is Obama and Hillary...Let's put Hillary at the top - That's a position she's familiar with," Limbaugh said on his radio show Thursday. "Therefore, you've got a woman and a black for the first time ever on the Democrat ticket. Ahem. They don't have a prayer."

Donna Brazile, Al Gores former presidential campaign manager, called the comments "un-American."

"I'm an American. And I'm proud to be an American," Brazile said on CNN's The Situation Room Wednesday. "But I think that comment is, as far as I can tell, a very un-American conversation, because African-Americans and women fight for this country. We have died for this country."

“To suggest, somehow or another, that we are not capable of serving this country in the capacity of Commander-in-Chief is just, in my mind, mind-boggling," she continued. "So, with all due respect to Mr. Limbaugh, just wait. Let the people decide. And I guarantee you, the people will make a better decision than Rush Limbaugh."

Limbaugh's comments came hours after Hillary Clinton said the Democratic presidential race could result in a joint ticket.

“That may be where this is headed,” she told CBS Wednesday morning. “But of course we have to decide who is on the top of ticket. I think the people of Ohio very clearly said that it should be me."

Obama later called any speculation of teaming up with Clinton "premature."

- CNN Ticker Producer Alexander Mooney