AJAX, Ont. -- Justin Trudeau is flatly ruling out a Liberal-NDP coalition to prevent Prime Minister Stephen Harper's Conservatives from forming another government if no party has a majority after the Oct. 19 vote.

"I do not believe in formal coalitions," Trudeau said Monday.

"The Liberal party is, of course, as it always has been, open to working with other parties elected in the House of Commons to pass the right legislation to help Canadians."

Campaigning on his plan to ease the government burden on middle-class paycheques , Trudeau dismissed the idea of governing in partnership with Tom Mulcair, saying the New Democrat leader has no plans for the economy.

"I don't believe in backroom deals or arrangements amongst leaders," Trudeau said at a campaign stop in suburban Ajax, Ont.

"I believe that Canadians should have the full range of choices so that they can pick the team with the better plan."

Trudeau said the NDP would also hike taxes on corporations, stalling economic growth, but would not have the courage to increase taxes on high income earners to help fund a tax cut for the middle class, said Trudeau.

A Liberal government would raise taxes on the richest Canadians while cutting taxes for those making between $44,000 and $89,000.

"You deserve a plan that offers real growth for the middle class, not just a different government, but a better one," he said.

"We will stop giving government cheques to wealthy families so we can give more to the middle class and lower-income families."

Speaking from one of the vote-rich communities that surround Toronto, Trudeau said the middle class has been neglected by Harper's Conservatives for nearly a decade.

"The Conservatives believe the way to grow the economy is to make wealthy people wealthier, to give the most to the people who need it the least," he said. "This is a tougher economy than it needs to be for the middle class and those who wish to join it. Mr. Harper doesn't see that from 24 Sussex (Drive)."

The Liberal leader also said his proposal for a new tax-free child benefit would put more money in the pockets of those who need it most.

Trudeau also got in another dig at Harper over the Mike Duffy scandal, saying it's time for the prime minister to come clean about the involvement of a number of his staff members, some of whom are working on the Conservative leader's election campaign.

"Mr. Harper's decision not just to promote and protect people who seem to have been at the heart of this cover-up, and keep them actively engaged in his campaign, really illustrates that Mr. Harper doesn't have much respect for the office that he holds or for the intelligence of Canadians."

Trudeau had only one other campaign event scheduled Monday, a rally with Ontario Premier Kathleen Wynne in downtown Toronto.

He brushed off questions about whether the police investigations into the Ontario government or Wynne's decision to privatize Hydro One could hurt the federal Liberals in the campaign.