Conservative leader Stephen Harper says some Liberal campaign ads are so offensive, he wants them yanked off the air. Harper says the ads promote anti-Americanism and are inappropriate.

The ads asks voters to choose between a country like Canada with generous social programs, or a country like the U.S. with its lower tax rates, referring to tax cuts proposed by Harper. 

"I think given the security situation it's not appropriate for any political party to do anything that would encourage anti-Americanism or break down that co-operation at this point," Harper said after U.S. officials announced an increased terrorist threat Wednesday.

But Martin's team said Harper's allegations are nonsense. "The ads aren't about America. They're about Stephen Harper," said Liberal spokesman Scott Reid.

Harper has said that over the long term, he would cut Canadian tax levels to at least those in the U.S.

Even if he's wrong on who the ads target, CTV's Craig Oliver said Harper presents a weak argument. "I'm not sure that I understand why it's anti-American for us during a course of a Canadian election campaign to discuss the differences in our two societies."

Oliver points out that the Liberals have moved in a very different direction compared to their American counterparts.

"In Washington, for instance, they're thinking of a constitutional amendment to
ban abortion. In this country, we're talking about people of the same sex can get married and can smoke marijuana to celebrate afterwards. And we made a really significant fundamental decision not to join the Americans in a war," Oliver said.