BRANTFORD, Ont. -- The NDP is the only party with the backbone to stand up to the Conservatives and walk away from the Trans-Pacific Partnership, party leader Tom Mulcair said Sunday as he embarked on a blitz of ridings in southwestern Ontario that went to the Tories in the last election.

On one of his most active campaign days to date, Mulcair honed in on the Liberal position on the trade talks in Atlanta. Specifically, he seized on comments by Liberal candidate Catherine McKenna, who on Saturday said her party was not willing to echo the NDP's position that they wouldn't feel tied to an agreement.

"Where was Justin Trudeau and his Liberals in all of this? Well, yesterday in Ottawa, they were saying that they had no choice but to back Stephen Harper's secretly negotiated deal for the Trans-Pacific Partnership," Mulcair said in Brantford, Ont., his first stop of the day.

"The NDP, when we form government on Oct. 19, will not be bound by this secret agreement that Mr. Harper has been negotiating."

Mulcair later spoke in front of about 300 people during another quick stop in Waterloo, Ont., where he implored the crowd to keep in mind what the Trans-Pacific Partnership could do to the region's farmers whose businesses could unravel.

"Think about the family that's been running that dairy farm for generations," he said.

Mulcair, who has been confronted with headlines in recent days that say the NDP has fallen behind in the polls, stressed that people seeking change have only one genuine option.

"Get tired of the Liberals and the sponsorship scandal? No problem, you're supposed to go back to the Conservatives. When you're tired of Stephen Harper's unblemished record of continuous corruption and a revolving door of favouritism and $90,000 cheques in the Prime Minister's Office? No problem, you're supposed to go back," he said.

"Hold on. This time, for the first time in our history, there's hope. We can get real change."

The whistle-stop tour is also intended to deliver the NDP's message that Harper has failed Ontario's agricultural and industrial heartland, long before the Trans-Pacific Partnership talks began.

Mulcair has repeatedly accused the Conservatives of enacting policies that cost 400,000 manufacturing jobs since the recession in 2008, including 43,000 in Canada's auto industry.

His campaign also includes stops in Stratford, London, Sarnia and Essex.

The NDP issued a handout that lists all the communities that Mulcair is visiting, with highlights beside each one showing the number of manufacturing jobs that the NDP says the communities have lost since the Conservatives came to power.