MONTREAL -- Paul Martin returned to the Liberal campaign trail Friday to lend credibility to Justin Trudeau's economic team in Quebec, but for a few moments, people could be forgiven for wondering who was running for prime minister.

The contrast between the seasoned campaigner and the young, telegenic leader was never more apparent than at an event in Martin's old Montreal riding, now renamed LaSalle-Emard-Verdun.

The former prime minister and finance minister, lionized by Liberals for taming the federal deficit in the 1990s, almost overshadowed Trudeau as he delivered a passionate, articulate denunciation of the Conservative fiscal record.

Martin sharpened his direct appeal to left-leaning voters made earlier in the week by accusing the NDP of siding with the Harper government on economic policy.

The public has grown used to the Harper government's mantra on deficits, but should be startled by what they hear from New Democrats, he said.

"That Tom Mulcair is now a student of Stephen Harper's economy makes absolutely no sense," said Martin.

"Where is the conscience of those who belong in the NDP? How can the NDP party -- those who've worked it for all these years -- stand for the fact that the party is now holding hands with the Conservatives and saying that our goal in the next mandate is to do absolutely nothing?"

He mocked Harper's animated response Thursday to the Liberal proposal to run "modest" shortfalls and said criticism of the plan was rich coming from a government that has added $150 billion to the national debt.

"He's the king of deficits," said Martin, whose remarks in English seemed aimed at an audience outside of Quebec.

"The current Conservative government has ground the economy down so far, trapping our most vulnerable of citizens in the process, that the next government has to act -- and that the NDP doesn't understand that boggles the mind.

"Conservative obsession with eliminating the deficit down to the final decimal point is more than short-sighted. It's yesterday's war."

NDP Leader Tom Mulcair, also in Montreal, said the Liberals shouldn't be labelling anybody when it comes to finances.

"Justin, when you're standing beside the king of austerity, Paul Martin -- the man who cut 24 per cent of social and health transfers to the provinces, who cut deeply into employment insurance and put an end to all federal spending in social housing -- could you be a little more discrete before you criticize the NDP's balanced, realistic approach to taking care of future generations?"

The Conservative campaign, in an attempt to rebut Liberal and NDP assertions that the country is in deficit now, pointed Friday to new Finance Department figures that say the federal treasury posted a $5-billion surplus for the first three months of the fiscal year.

Trudeau, whose pitch was delivered mostly in French, attempted to frame the ballot box question for Quebec voters "as a choice between jobs, investment and growth or cuts and cuts and cuts."

Conservative attacks and now even NDP political messaging have tried to define Trudeau as out of his depth on the economy and "not ready" to lead the country. To counter that perception, Liberals gathered candidates from across the country in Toronto this week, pointing to a roster of impressive resumes in business, finance and public service, to demonstrate they have a competent "team."

They attempted to replicate that for the Quebec audience on Friday.

Liberals emphasized the party's recently announced infrastructure platform, which proposes to invest as much as $125 billion to fix crumbling roads and bridges.

Trudeau put particular emphasis on public transit and investments in early learning and childhood development -- issues that have been front and centre in the province.