Toronto, Dec 16 (IANS) Canadian politics sunk to a new low this week when the opposition Liberal Party posted on its website a doctored picture of Prime Minister Stephen Harper being assassinated.

After an uproar, the opposition party removed the offending photo which showed the prime minister's face superimposed on the picture of Lee Harvey Oswald - alleged killer of American President John F. Kennedy in 1963 - being gunned down by Jack Ruby.

The opposition party's website also carried another photo of the prime minister which showed his arm thrust to the elbow in the wrong end of a cow.

Opposition (Liberal Party) spokesman Daniel Lauzon maintained that all photos were screened by the party before being posted.

He said the pictures of the prime minister were removed "due to the possibility of misinterpretation" in the public.

"We do review them but that one (showing the prime minister being assassinated) admittedly slipped through the cracks," the Canadian Press quoted the opposition spokesman as saying.

"We removed it immediately and we apologise to anyone who was offended," he said.

But the cow picture, he said, was meant to poke fun at the carbon emissions produced by bovine flatulence. He said his party had invited people to post such pictures to make fun of the prime minister's reluctance to go to the on-going Copenhagen climate-change summit.

The opposition spokesman described the photos as 'user-generated', not reflecting the views of his party.

The Prime Minister's Office in Ottawa refused to comment on the offending pictures.

"We won't dignify this with a response," PMO spokesman Dimitri Soudas was quoted as saying.

He said it is the leader of the Liberal party (Michael Ignatieff) who "should comment, not us, as the incident reflects" on his judgment.