OTTAWA -- The autumn session of Canada's parliament began on an innocuous note, with both sides of the chamber agreeing in an uncharacteristic spirit of bipartisanship that coins tossed into the Gothic capitol's centennial fountain should be used to aid the disabled.

Then Prime Minister Brian Mulroney walked into the packed House of Commons for the traditional hour of members' questions this week, and reality came crashing down on the beleaguered Conservative Party leader.

"Canadians would like to know where you have been hiding, Mr. Prime Minister. Why are you abandoning your responsibility?" asked Ethel Blondin, a Liberal Party member from the Northwest Territories and one of the house's most vocal advocates of Indian rights.

The question obliquely alluded to Mulroney's summer-long reclusion at his Harrington Lake vacation home, perhaps to contemplate the failure of his planned constitutional reforms, mounting economic problems and a wave of militancy by Canada's recently politicized Indian minority.

Both supporters and critics of the prime minister describe a growing cynicism and antipathy directed not so much at Mulroney's policies as his personal credibility and integrity.

Mulroney was elected in 1984 with the largest plurality in Canada's history and reelected four years later with another commanding majority. Now, with an approval rating of as low as 12 percent in some opinion polls, he seems likely to serve the last two years of his term engulfed in controversy.

When heavily armed Mohawk Indians erected barricades around a golf course in a Montreal suburb and a police officer was killed in a shootout last July, the government opted to avoid further bloodshed and attempted to negotiate the Mohawks' surrender. Talks on Indian land claims, which go back hundreds of years, were to follow.

It seemed like a prudent strategy at the time, but the handful of holdout Mohawks who were besieged by Canadian army troops at Oka, Quebec, until surrendering yesterday succeeded not only in thrusting the issue of native rights to the forefront of national debate, but in portraying Mulroney's government as paralyzed by indecision.

Early this year, Mulroney guided through the House of Commons a 7 percent value-added tax as the key economic initiative of his ministership. His economists said it was essential for reducing the government's mounting deficit and reversing a slide into economic recession.

But with polls indicating that 80 percent of Canadians oppose the tax, which would be on virtually all goods and services, the appointed Senate has taken steps to override the will of the elected House of Commons and block the measure.

It would be the first time in 30 years that the Senate vetoed a money bill. The last time the chamber refused to pass government legislation was when it balked at the U.S.-Canada free trade agreement and forced the 1988 election.

The Liberals, largely as a result of appointments made by former prime minister Pierre Elliott Trudeau, hold 52 seats in the Senate and the Conservatives' 46. So, to ensure the bill's passage, Mulroney in the last month has named 15 Conservatives to fill vacancies in the Senate and has vowed to invoke a never-used constitutional clause to expand the chamber with an additional eight Conservatives.

Mulroney already had been unapologetic in the face of rising public indignation over his appointment to the Senate of former Nova Scotia premier John Buchanan, who earlier this month resigned in the middle of a police investigation into allegations that he channeled government contracts to political allies.

"We'll use every democratic and constitutional means to assure that our political agenda -- which won the last election -- passes," Mulroney said.

The undisguised attempt to pack the Senate with Conservatives has resulted in another chorus of public indignation. But the prime minister insists he will expand the upper chamber anyway because an appointed, patronage-based body should not be allowed to reverse decisions made by the elected House of Commons.

It is a measure of the public antipathy for Mulroney, and the unpopularity of the proposed value-added tax, that opinion could swing so dramatically against the prime minister in favor of an institution so widely derided by Canadians as an ineffectual and money-wasting bastion of political favoritism.

The battle over the federal tax has become a debate on the legitimacy of the country's legislative process at a time when the country is still debating the relationship between the federal government and the predominantly French-speaking province of Quebec.

Mulroney, who was elected largely on the promise of harmonizing divergent views on Canada's identity and the meaning of its 123-year-old confederation, witnessed last April the collapse of constitutional reform intended to unify Quebec with English-speaking Canada.

The Quebec separatist movement is certain to reemerge at the instigation of a new parliamentary voting bloc of nine defected Liberal and Conservative French speakers, called the Bloc Quebecois. Mulroney then could face an ongoing constitutional crisis.

But if the prime minister is feeling overwhelmed by his mounting political problems, he is not showing it. During Tuesday's parliamentary question period, the opposition New Democratic Party leader, Audrey McLaughlin, sarcastically asked Mulroney why he did not simply kill the goods-and-services tax "instead of going on another binge of political patronage appointments."

Mulroney shot up from his front row seat, his temper showing for a moment. Then he smiled and observed that one thing he had noticed during his political career was that the opposition always is against patronage -- until it is offered.