Prime Minister Stephen Harper made an unprecedented appearance Thursday before a special Senate committee examining his proposal for shortening the term of senators.

Harper wants new appointees limited to terms of eight years. Senators currently sit for as many as 45 years before being compelled to retire at 75.

There were some tense moments during Harper's appearance, and one senator compared his firm stance to a former Liberal prime minister.

Senator Jim Munson told Harper that "there are critics who believe you would like nothing better than to fight an election on the backs of the Senate."

Harper responded: "Well, don't give me the opportunity."

Munro then told Harper his statement reminded him of Pierre Trudeau's famous phrase, "Just watch me."

The reform would eliminate Canadians' ability to refer to senators as "lifers," Harper told the Senate committee.

"The government is not looking for another report, we are seeking action," he said.

While the proposed reform calls for limiting senators' terms to eight years, the government is flexible and would consider six or even nine years, as some have proposed, Harper said -- as long as there is a limit.

"We are seeking limited, fixed terms of office," he said.

Canada needs an upper house with democratic legitimacy, the prime minister said.

Harper said it's become a convention for politicians to promise Senate reform during elections, but to date no one has followed through once elected.

"This has to end, because the Senate must change. We will be the authors of that change," he vowed.

Liberal strategists suspect the prime minister's move is meant to be a warning to the Liberal-dominated Senate that Harper won't tolerate any attempt by unelected senators to derail legislation on issues he feels strongly for. That includes his Federal Accountability Act.

The act, aimed at cleaning up government in the wake of the Liberal-era sponsorship scandal, is currently under study by the Senate's legal and constitutional affairs committee.

On Tuesday, Liberals on the committee blocked a Conservative effort to conclude hearings by Sept. 26.

Liberal senators are insisting the act needs significant revisions, an insistence that could lead to an impasse by the Harper government that would only be broken by an election.

Tory strategists, however, predict Liberals will back down rather than risk declining popularity in another election because the sponsorship scandal is still fresh on the minds of voters.

Liberal senators will also test the Senate reform, as some suggest the proposal is unconstitutional and should be heard before the Supreme Court of Canada first.

The government insists its proposal requires only the approval of both houses of Parliament, but Liberal Senator Jack Austin suggested a constitutional amendment with provincial consent would be needed.

Seeking to head off that argument, the prime minister reminded the Senate committee that the 1984 Molgat Cosgrove report on Senate reform made a similar recommendation regarding term length, and "confirmed that such a change was achievable without using the general constitutional amending formula."

Harper's appearance before the committee was the first of a sitting prime minister.

With a report from CTV's Robert Fife and files from The Canadian Press