Speaking at a Bombardier plant in Thunder Bay, the Horwath touted her party's Buy Ontario plan, which critics have blasted as a protectionist policy that would hamper industry.
"You can label it whatever you want, but I call it a job creation program that puts Ontario tax dollars to work and puts Ontario workers to work," she said.
Horwath also rejected Liberal accusations that she voted against transit investments that would have brought work to the north, saying the proposals were buried in omnibus budget bills.
"When I vote against budgets, it's usually because they're full of a bunch of things I don't support, things like the harmonized sales tax," she said.
Liberal Michael Gravelle, the incumbent in the riding of Thunder Bay-Superior North, said Horwath's votes to pan the 2006 and 2008 budgets could have killed the Thunder Bay plant.
"If Andrea Horwath had her way, there would be no new subway cars, no new GO trains, and no good-paying jobs at Bombardier," Gravelle said in a statement Friday.
"The NDP talks the talk in northern Ontario, but does the exact opposite in Toronto," he said.
Liberal Leader Dalton McGuinty accused Horwath earlier this week of trying to block development in the north, and his party has argued the NDP's northern platform will cost the struggling region jobs.
The Progressive Conservatives have instead attacked the party's plan to eliminate corporate tax cuts, saying it will deter companies from investing in Ontario and creating new jobs.
Horwath, who is on her second tour of the north since the campaign started last week, took issue with the premier's comments.
"If he wants to challenge my commitment to northern Ontario, if he wants to have a real debate about the issues that face northerners, then he should come to the north and have that debate," said Horwath.
Horwath has been pushing for a debate in the north for weeks, saying issues such as unemployment and the high cost of living in that area deserve their own turn in the spotlight.
Tory Leader Tim Hudak and Horwath have agreed to participate in a northern debate, but McGuinty has said he'd rather discuss northern issues during the televised leaders' debate in Toronto on Sept. 27.
The Buy Ontario program is a key part of the party's plan to create and protect jobs — particularly those in manufacturing — in northern Ontario.
It would force public organizations to buy Ontario products for their projects as long as there are some available at a cost within 10 per cent of competing products.
They would otherwise have to buy Canadian products at a cost within five per cent.
Ontario products would be defined as any product where more than half the value is manufactured, produced or assembled in Ontario.
The plan builds on existing provincial regulations that call for 25 per cent of vehicle costs for transit projects to go to Canadian companies.
Exemptions would be made when a required product simply isn't manufactured or processed domestically, "but it's the exception, not the rule," Horwath said.
Horwath toured the Thunder Bay plant a day after McGuinty, who visited with CAW President Ken Lewenza at his side.
The NDP brushed off any suggestion Friday that Lewenza's absence signals dwindling support from the auto workers union.
The plant is building hundreds of subway and streetcar wagons meant for Toronto, a contract Bombardier has said will lead to thousands of new jobs.
Horwath said the plant is proof Buy Ontario efforts work, and condemned the Liberals for allowing another transit contract to leave the province.
Metrolinx, a provincial agency, recently awarded a $120-million contract to refurbish GO Transit trains to a Quebec company.
Ontario Northland, a company based in North Bay — where Horwath was headed later Friday — made a bid $2.1 million higher.
The Ontario Chamber of Commerce has said it supports a stronger Buy Ontario system.
If elected, Horwath is promising to create a northern Ontario committee at the legislature, made up solely of members from the north, which would investigate issues such as forestry, energy and mining and make recommendations to the government. All legislation affecting northern Ontario would be referred to that committee for review, which will ensure northerners have a say.
The NDP also wants to make industrial hydro rates more competitive by expanding a program that allows companies to shift operations to lower peak times, reducing hydro costs. Smaller mines and sawmills would also be allowed to join the program.
They would also spend $300 million over three years to extend a northern Ontario industrial electricity rate program, set to expire in 2013, all in exchange for job guarantees.