Stephen Harper is dismissing Justin Trudeau's Senate reform plan as cosmetic change, rather than attempting to match or top his rival's new proposal.

Mr. Trudeau, the Liberal Leader, took Canadian politics by surprise Wednesday morning when he announced that he was expelling all Liberal senators from his parliamentary caucus and would advocate a non-partisan process for appointing future senators that would fill the Senate with independents.

The Conservative Prime Minister, whose own Senate reform plans are stalled while he awaits a Supreme Court decision on whether he can proceed, derided the Trudeau plan by saying it would do nothing to make the Red Chamber more democratic and accountable.

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"What the Liberal Party doesn't understand is that Canadians are not looking for a better unelected Senate," Mr. Harper told the Commons during Question Period Wednesday. "Canadians believe that for the Senate to be meaningful in the 21st century it must be elected."

Added Mr. Harper: "I gather the change announced by the Liberal Leader today is that unelected Liberal senators will become unelected senators who happen to be Liberal."

The Conservatives plan to dispatch Democratic Reform minister Pierre Poilievre repeatedly in the weeks ahead to attack the Liberal proposal as elitist and undemocratic.

The Harper government, which still has hopes for electing senators, has asked the Supreme Court to rule on what degree of independence Parliament possesses in making a series of reforms to the Red Chamber. The Conservatives say if they can't make their reforms, they would favour abolishing the Senate instead.

The Supreme Court is expected to decide this year on whether Parliament by itself can impose term limits on senators, whether Parliament or the provinces can consult the public on recommendations for Senate appointments – such as ballots – and whether Parliament can abolish the Red Chamber without the approval of all provinces.

Taunting Mr. Harper, Mr. Trudeau said Wednesday that the Tory Leader no longer needs to wait for judges to rule. "The Liberals have taken action … to remove partisanship and patronage from the Senate," the Liberal chief said.

Mr. Harper countered by noting that the Liberal leader in the Senate, Senator James Cowan, had assured reporters that the change was minimal. "I suspect that not a great deal will change," Mr. Cowan said Wednesday.

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NDP Leader Thomas Mulcair said Mr. Harper's tough talk about the need for an elected Senate would be more impactful "were it not for the fact that the Prime Minister has broken Brian Mulroney's record for naming unelected senators: 59 in total."

The Conservative Leader shot back that the "only problem the NDP has with senators is that it doesn't have any senators."

Mr. Mulcair's response: "And we're quite proud of that."

Conservative government sources speculate that Mr. Trudeau has an ulterior motive for his Wednesday reform announcement, which includes expelling all Liberal senators from the party's parliamentary caucus. Tories suggest this is a pre-emptive strike because the Liberals are nervous that more Liberal senators will be caught up in the Senate spending scandal after the Auditor-General tables a pending review of spending in the Red Chamber.

The Senate expenses scandal has dogged the Harper government for more than 10 months because the majority of controversial cases concern Conservative appointees to the chamber, including Mike Duffy, Pamela Wallin and Patrick Brazeau.

The RCMP is investigating the matter.