TORONTO - Labour leaders are warning that an already hot spring of worker discontent could blow into full-scale chaos if governments fail to help stem a loss of manufacturing jobs they say has reached crisis proportions in Canada's industrial heartland.

Plant occupations this week and rallies planned for Sunday and another at the end of the month on Parliament Hill could be just a taste of what's to come, union leaders say.

"Nobody seems to be recognizing that we've got a crisis in manufacturing in the country," says Buzz Hargrove, president of the Canadian Auto Workers.

"We're hoping that the demonstrations . . . will draw attention to the crisis."

Union leaders say about a quarter of a million well-paying manufacturing jobs have vanished over the last five years, devastating families and even whole communities.

The national unemployment rate is at a 33-year low of 6.1 per cent, but labour officials say new jobs tend to be part-time or temporary, offering lower pay, fewer if any benefits, and no security.

The auto industry alone has bled 17,000 jobs in assembly and parts in the past two years, with more to come.

"Workers are frustrated, they're getting angry," said Wayne Fraser, director of the United Steelworkers, whose members protested in 10 Ontario cities this week to draw attention to the issue.

"The province this summer is going to be in chaos."

Labour leaders are divided on where the blame should lie.

For Hargrove, the villain is the strength of the Canadian dollar combined with federal policies he says allow too many imported vehicles into the country.

"I don't think there's anybody in the country who would say our dollar is at its natural level," Hargrove said.

"It really is being driven by oil and gas, which is harming the rest of the economy."

While Hargrove praises the Ontario Liberal government of Dalton McGuinty, other unions are incensed at what they see as the premier's indifference to the job cuts.

From McGuinty's perspective, "This is a challenge we're facing throughout North America and we will continue to experience this in an era of globalization."

However, he added in Ottawa this week: "If you take all of the jobs we've lost and all the jobs we've gained in the last 3� years, we're ahead by 320,000 net new jobs. So we've come out on the upside."

Wayne Samuelson, president of the Ontario Federation of Labour, calls the premier's attitude insulting.

"McGuinty won't even recognize there's a problem," Samuelson said as he prepared to fly to Thunder Bay, Ont., for another job-loss forum.

Some northern Ontario communities have been "wiped out" by mill and plant closures.

"Companies shouldn't be able to just sort of quietly load up their limos with dough and leave town," Samuelson said. "There should be a real debate about why that factory is closing."

McGuinty conceded the forestry sector is facing "real challenges" but said his government has put in nearly $1 billion to help. The province has also created a $500-million fund for manufacturing industries and put up an additional $500 million for the auto sector, he noted.

Ontario Trade Minister Sandra Pupatello said "manufacturing is really struggling" because of global competitive pressures and insisted Ottawa must do its part as well.

"We are desperate to have all hands at the table," Pupatello said.

"It can't be just the provincial government, and that's frankly currently what we've been facing."

Manufacturers say they're operating in a tough environment and offer little comfort to employees worried about the future.

"I don't know if there's a crisis - there's a significant challenge for manufacturing, particularly in Ontario," said Jay Myers, chief economist for Canadian Manufacturers and Exporters.

"If the dollar continues to rise, costs are going up, with the state of competitiveness out there, we will see job losses and plant closures."

Myers said the federal government, which announces its manufacturing strategy on Tuesday, has helped with its accelerated two-year writeoff for machinery and equipment but more is needed.

"What the government can do is try to cut costs as much as they can for manufacturers, but to a large extent, it's up to manufacturers and management and labour themselves to adjust to the new reality out here."