Justin Trudeau offered a new tax credit for teachers' school expenses on Wednesday, while promising investment and growth, rather than echoing his rivals' pledges to balance the budget.

"The economy needs investment," Trudeau said at a campaign stop in Newmarket, Ont., when asked if he would balance the budget this year. His chief opponents, NDP Leader Thomas Mulcair and Conservative Leader Stephen Harper, have already pledged to balance the budget if elected in October.

Trudeau slammed both his opponents for their economic policies. He compared Harper's economic record to that of Depression-era Prime Minister R.B. Bennett, then accused Mulcair of being "disingenuous" with campaign promises he can't afford to pay for while balancing the budget.

"Mr. Mulcair is going to have to come clean on which promises he's going to be dropping," Trudeau said.

The Liberal Leader insisted the economy needs "investment" in order to weather the current economic uncertainty, and offered a new teacher tax credit as an example.

The credit Trudeau proposed Wednesday would be aimed at helping educators cover their "out of pocket" expenses in the classroom, by allowing teachers to claim up to $150 in cash per year for up to $1,000 spent on school supplies and educational materials.

Trudeau said all teachers would have access to the tax credit, regardless of their income.

The credit would allow teachers to claim expenses for items like motivational stickers, Bristol boards, supplementary books, science experiment supplies and even big-ticket items like tablets, laptops and classroom projectors.

Speaking at his own campaign event on Wednesday, Harper called Trudeau's proposed credit an "attempt to ape" his own party's policies. "It certainly sounds a lot like trying to be a Conservative," Harper said.

The tax credit is based on a similar one offered in Prince Edward Island.