"Austan Goolsbee secretly sending messages to the Canadian government, elements of the Canadian government, that the criticism of NAFTA should not be taken seriously," Wolfson said. "Very simple question — it deserves a very simple answer: Has Austan Goolsbee had any contact with anyone in the Canadian government or the embassy to send such a message?"
Before the Clinton campaign's call, the Obama campaign stood by its previous denials of any outreach from the Obama campaign to the Canadian government, but would not specifically address reports of a conversation between Goolsbee and the Canadian official.
"It's telling that the Clinton campaign's closing argument is based on a story run on a Canadian television station that's already been debunked by the Canadian Embassy," Obama campaign spokesman Bill Burton said.
"Again, this story is not true. There was no one at any level of our campaign, at any point, anywhere, who said or otherwise implied Obama was backing away from his consistent position on trade. The only flip-flopping on NAFTA has come from Sen. Clinton, who talked about how good it was for America until she started running for President," Burton said.
The free trade agreement, signed into law by former President Clinton, is highly controversial in the crucial March 4 voting state of Ohio, where it is blamed for job losses.
The Canadian government supports NAFTA and says it has reached out to U.S. presidential candidates to make its case.
"We do have diplomatic representatives posted in many places in the U.S. and these representatives are actively talking to decision makers in the U.S. and that includes people who are involved on the campaigns," said Tristan Landry, a spokesman for the Canadian Embassy in Washington, D.C.
"At no point did any member of a presidential campaign call the Canadian ambassador or any official working for this embassy to discuss NAFTA. That is simply not true," he said.
The Canadian government says NAFTA is responsible for creating 7 million jobs within the United States.
Sen. John McCain, R-Ariz., suggested today that Obama's and Clinton's threats to walk away from the treaty could threaten Canadian military help in Afghanistan.
"If we announce that we're going to unilaterally change a treaty or suspend it … obviously that I think it can affect Canadian public opinion adversely, in fact I've been told that by my Canadian friends and colleagues," he told reporters after a town hall meeting at the corporate headquarters of Dell Inc.
"The Canadians are now supplying brave young Canadians to the fight in Afghanistan. One of our priorities is to try to get more cooperation from our allies throughout the world."
"All these things are interconnected," he said, suggesting such a demand would affect Canadian public opinion, which "could have an adverse affect on the situation with regards to their commitment to Afghanistan which we all know is a matter of controversy among the Canadian people."
ABC News' Jake Tapper contributed reporting.