Ahead of elections in October, Harper's Liberal opponents seized on the incident to tie Harper to former Australian prime minister John Howard and US President George W. Bush, who were close allies in the "war on terror."

Harper's former speechwriter Owen Lippert claimed responsibility for the gaffe and resigned from his job as a researcher for the Conservative Party.

In a statement, the staffer apologised for being "overzealous in copying segments of another world leader's speech" and said his bosses at the time were unaware he had done so.

Liberal Member of Parliament Bob Rae suggested the speech was "more evidence" of Harper's foreign policies being in "lock-step with the right-wing foreign policy of the Bush administration."

For that and for plagiarism, "Harper has to go," said Liberal leader Stephane Dion.

Conservative Party spokesman Dan Dugas said the "five-year-old speech" was no longer relevant.

"This Conservative government is focused on the economy and the stewardship of the country's finances ... which is what mostly concerns voters now," he said.

Speaking in parliament on March 20, 2003, Harper, then in opposition, delivered an almost "verbatim copy" of a speech by Australia's John Howard two days earlier, the Liberals said.

"How does a leader in Canada's parliament, on such a crucial issue, end up giving almost the exact same speech as any another country's leader, let alone a leader who was a key member of George W. Bush's coalition of the willing?" said Rae.

"Liberals have been arguing for over two years that Canada is losing its independent voice in foreign affairs under Mr. Harper," he said. "We just had no idea that Mr. Harper was prepared to borrow the drafting of the actual words he would use from another country."