TORONTO, DEC. 13 -- After months of raucous debate that at times called into question the future of Canada's bicameral legislative process, the appointed Senate today approved a controversial federal sales tax aimed at reducing the country's mounting deficit.

The 7 percent value-added tax on most goods and services, which will be applied Jan. 1 on top of existing provincial sales taxes of up to 10 percent, is the key economic initiative of Prime Minister Brian Mulroney's government.

Mulroney has said defeat of the measure would have added some $7 billion (Canadian) to the nation's $30 billion budget deficit.

The 55-to-49 vote was along party lines. Mulroney's Conservative Party holds a majority in the Senate, achieved in September with the unprecedented addition of eight new seats by Britain's Queen Elizabeth II.

The vote came after Conservatives cut off filibustering and procedural delays by opposition Liberals by ramming through a disputed rules change.

The Liberals in the Senate -- known as the "chamber of sober, second thought" -- had used bicycle horns and kazoos to disrupt proceedings and express their outrage at what they said was a railroading of the tax measure.

The tax is opposed by 80 percent of Canadians, according to some polls.

Shouts of "Gangster!" and "Criminal!" erupted through the stately, red-carpeted chamber as Liberal senators kicked waste baskets and pounded on their desks to protest Speaker Guy Charbonneau's decision to push aside further delaying tactics by the opposition and proceed with a vote on the measure.

To reverse the Liberals' majority in the Senate, Mulroney prevailed on the British monarch, who is still nominally sovereign of Canada as well, to invoke an obscure clause in the constitution and authorize him to pack the chamber with Conservative appointees.

The move triggered a furious national debate on the legitimacy of Canada's legislative process and revived calls for an overhaul of Parliament to include an elected Senate along the lines of that in the United States.

Mulroney today formally introduced a measure creating a parliamentary commission that will study ways to amend the country's 1982 constitution.

Suggested amendments, which Mulroney said might be put to a national referendum, include reforming the Senate.