Should the Conservatives make good on their promise to introduce income splitting for couples with children under 18 before the next federal election, Justin Trudeau says a Liberal government would move to reverse that decision.

Trudeau, who was in Toronto to promote his newly published memoir Common Ground, which he's released ahead of next year's federal election, spoke to CBC News on Monday morning.

Asked what tax measures he would specifically look to reverse, Trudeau pointed to Stephen Harper's proposal to introduce income splitting once the deficit is eliminated.

"We've been talking about the income-splitting measure that the government has proposed recently."

"It doesn't help the people who need it most and it costs Canadians an awful lot to do. It doesn't make sense," Trudeau said in a telephone interview.

Trudeau made it clear during an interview with Radio-Canada's Les Coulisses du Pouvoir on Sunday he would not reverse pension splitting for seniors — a separate tax measure the Conservatives introduced in 2007.

Trudeau has already said a Liberal government would reverse the Harper government's decision to raise the age of eligibility for Old Age Security from 65 to 67.

On Monday, he also left the door open to reversing other tax relief measures.

"We're going to look at various proposals, but the fact is we need to make sure we are helping Canadians in the best possible way. I look forward to seeing what this government proposes in the upcoming update and budget, and we'll evaluate each initiative," the Liberal leader said.

The Conservatives first promised to bring in income splitting for couples with children under 18 during the 2011 federal election campaign, but have since seen their caucus divided on the issue.

The late finance minister Jim Flaherty backed away from the proposal in February when he said it would appear to only benefit a small number of Canadians.

"It's an interesting idea. I'm just one voice. It benefits some parts of the Canadian population a lot. And other parts of the Canadian population virtually not at all," Flaherty told reporters following an event in Ottawa.

Harper made it clear, two weeks later, the government was still committed to its income-splitting promise.

"As I said during the election campaign, we think income splitting would be an excellent policy for Canadian families just as it has been an excellent policy for Canadian seniors," the prime minister told the Commons at the end of February.

Last month, Trudeau also criticized the Conservative government's announcement to cut employment insurance premiums for small businesses.