A campaign worker for the Conservatives has resigned, after the Liberals showed a 2003 speech by Stephen Harper that plagiarized sections of an address by then-Australian prime minister John Howard.

"In 2003, I worked in the Office of the Leader of the Opposition. I was tasked with -- and wrote -- a speech for the then Leader of the Opposition," Owen Lippert said in a press release issued Tuesday. "Pressed for time, I was overzealous in copying segments of another world leader's speech. Neither my superiors in the Office of the Leader of the Opposition nor the Leader of the Opposition was aware that I had done so."

Lippert, who also became a senior policy advisor for the Canadian International Development Agency in 2008, apologized to "all involved."

Just hours before Lippert's resignation, Liberal candidate Bob Rae accused Harper of plagiarizing almost half of Howard's speech, when Harper was opposition leader of the Canadian Alliance

At a press conference, Rae showed video of Harper giving a speech in Parliament on March 20, 2003 -- the first day U.S. forces began bombing Baghdad.

The video is contrasted with a speech two days earlier from Howard, in which he gives a strikingly similar address.

Much of Harper's address matches Howard's virtually word-for-word.

Rae released transcripts and videos of both speeches and suggested they serve as evidence that a vote for the Conservatives is akin to voting for a "Republican-Conservative" government.

"This is a disgraceful performance by the leader of a political party there for all the world to see, and all the world is going to see it. They need to see it because they need to know what we're dealing with here," Rae told CTV Newsnet.

"I would say 35 to 40 per cent of the speech is the same, word for word, statement for statement, paragraph for paragraph, as the speech that was given a day and a half earlier by Mr. Howard."

Meanwhile, the Tories are dismissing the allegations saying the "speech was given by a person who was leading a party that doesn't exist anymore," CTV's Graham Richardson reported Tuesday.

Richardson, discussing what was discussed in a conference call Tuesday with the Tories, said the party has no explanation for where the speech came from.

Tory officials said there's been a 100 per cent staff turnover since the speech, suggesting they don't know the source, said Richardson.

They're also saying they won't answer the question because it's "irrelevant," he said.

The Tories further dismissed suggestions that Harper received talking points from the Republicans in the U.S.

Rae, the Liberal foreign affairs critic, said the revelation raises questions about whether Harper's foreign policy views can be trusted.

"On this critical issue, on this issue on the world stage, this is a man who chose to parrot and to mimic and beg, borrow, steal someone else's voice," Rae said.

He added: "In law and journalism, in politics, if we can't speak with an authentic voice, who the hell are we?"

Rae said even Harper's opponents at the time acknowledged that the speech was eloquent. But he questioned how Harper could have dealt with such an important issue, using someone else's words.

"He made that choice so blindly and carelessly that he ended up delivering a word-for-word repetition of someone else's words and thoughts," Rae said.

CTV's Roger Smith called the revelations "the Liberal play of the day, the Hail Mary" designed to hurt the Conservatives' election campaign.

"The Liberals are using this to show that Stephen Harper is totally in lockstep with the coalition of the willing, with George Bush and his Australian allies on the war in Iraq and that his foreign policy is copycat policy of Washington," Smith said.

"Bob Rae went on to say Stephen Harper would have been expelled from high school for plagiarism."