OTTAWA/SURREY, British Columbia (Reuters) - The United States made an unprecedented foray into Canada's election campaign on Tuesday, warning politicians not to bash Washington in their bid to win the January 23 election. But an unapologetic Liberal Prime Minister Paul Martin responded immediately by saying "c'est la vie" -- that's life -- if the United States did not like his remarks, and he would not accept anyone telling him he cannot defend his country. In a hard-hitting speech in Ottawa, U.S. Ambassador David Wilkins lamented what he called relentless and incessant criticism of his country, which he speculated might begin to sow doubt about the strength of the binational relationship. "Canada never has to tear the United States down to build itself up," Wilkins said. "It may be smart election politics to thump your chest and constantly criticize your friend and your No. 1 trading partner. But it's a slippery slope and all of us should hope it doesn't have a long-term impact on our relationship." Wilkins did not name the prime minister directly, but he specifically targeted a comment made last week at the Montreal climate change conference in which Martin called on the United States to heed a "global conscience" and join efforts to combat global warming. That remark -- on top of criticism of U.S. policy on lumber, guns, passports and Iraq -- appeared to have riled the White House the most, particularly since Canada has a proportionally worse record than the United States on reining in greenhouse gas emissions. "I would respectfully submit to you that when it comes to a 'global conscience' the United States is walking the walk," Wilkins said, addressing the Canadian Club of Ottawa. "And when it comes to climate change, we are making significant progress, greater progress than many of those who have been most critical of the U.S." In the campaign for the June 2004 election Martin regularly said Canada did not want U.S.-style health care, fiscal deficits, taxes or attack ads. But in the last several months, particularly in frustration over U.S. refusal to eliminate duties on Canadian softwood, he has made more direct attacks on U.S. policy, and continued to do so during the election campaign. Martin refused to back down on Tuesday in Surrey, British Columbia. "That our friends do not like what we say -- well, c'est la vie. I'm going to defend Canada and I'm right on softwood lumber and I'm right on climate change and I won't let anybody tell me that I should not defend my country," he said. He also dismissed the idea that he was trying to single out Washington as part of his election campaign. "I have not made the United States or any country a target in this campaign," he said, noting that he had outlined Canada's stand on softwood lumber and climate change long before the election was called. Martin, whose minority government was brought down on November 28 after an official report detailed Liberal kickbacks which were used in election campaigns, currently leads Conservative leader Stephen Harper in the polls but not by enough to regain a majority in Parliament.