The 39-year-old centrist said his victory in Sunday's first round of voting was proof that pollsters -- who had long placed him second to Le Pen in the opening round -- "get it wrong".
"Nothing's won yet," Macron said during a visit to a hospital near Paris.
"I will continue to fight for two weeks... I will defend the progressive camp to the end," the ex-banker bidding to become France's youngest-ever president said.
Earlier, President Francois Hollande appeared to admonish his former economy minister for not taking the fight to Le Pen over the past two days.
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Le Pen, 48, was first out of the blocks after the first round, visiting Paris' main wholesale food market and giving a TV interview in which she accused the pro-EU Macron of representing "runaway globalisation" and lacking love for his country.
"We need to be extremely serious and mobilised, and not to think it's a done deal, because a vote is earned, it's fought for," said Hollande, who on Monday had urged voters to back Macron and called Le Pen a "risk" for France.
After winning Sunday's contest with 24.1 percent to Le Pen's 21.3 percent, Macron gave an exuberant victory speech followed by a high-profile celebration at a famous Paris bistrot, drawing fire from some.
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Socialist Party boss Jean-Christophe Cambadelis told French radio: "He was smug. He wrongly thought that it was a done deal. It's not a done deal."
Le Pen herself joined the bashing, saying "all French people saw that he had the feeling he'd already won. It's not very respectful of democracy, of the voters".
Macron defended the bistrot gathering in a France 2 television interview on Tuesday evening.
"I have no regrets. I take full responsibility," he said firmly, adding his guests were mostly campaigners who deserved a night out after a year of tireless work.
Turbo-charged
Since securing her berth in the runoff, Le Pen has turbo-charged her campaign with a string of appearances and statements, leaving her opponent on the back foot.
At the crack of dawn on Tuesday she was at the sprawling Rungis food market outside Paris, taking aim at what she said was Macron's desire for "total deregulation, total opening up, total free trade".
In contrast, her opponent has huddled in strategy meetings over June legislative elections that will determine the shape of a future Macron government.
WATCH: Le Pen steps down as National Front leader
Polls suggest that Macron will trounce Le Pen in the runoff with a margin of some 20 points.
But after the political shocks of Britain's vote to leave the European Union and Donald Trump's unlikely ascent to the White House, analysts say a late surge by Le Pen is still possible.
Le Pen says she is the only candidate for change in a deeply divided country burdened by high unemployment and inequality.
Le Pen said Monday she was quitting temporarily as head of her National Front (FN) party in order to concentrate on the campaign.
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The move was seen as largely symbolic but one that would loosen her association with the FN, the party founded by Le Pen's father, Jean-Marie, notorious for anti-Semitic and xenophobic remarks.
On Tuesday, Le Pen gained an indirect boost from a conservative activist group called Manif pour Tous ("Protest for Everyone") that in 2013 staged mass rallies against same-sex marriage, a cornerstone law pushed through by Hollande.
In a statement that made no reference to Le Pen, Manif pour Tous leader Ludovine de la Rochere urged supporters to say "no" to Macron, an "openly anti-family candidate."
Homage to slain policeman
Earlier Tuesday, the rival candidates attended a sombre ceremony honouring a policeman killed on the Champs-Elysees last week.
Macron and Le Pen stood grim-faced among hundreds of mourners as Xavier Jugele's gay partner delivered a moving eulogy to the 37-year-old officer, whose shooting was claimed by the Islamic State group.
Macron and Le Pen differ starkly on how to protect France, still reeling from a string of jihadist attacks since 2015 that has claimed more than 230 lives.
Le Pen has called for France to take back control of its borders from the European Union and deport all foreigners on a terror watchlist, accusing Macron of being soft on terrorism.
Macron has urged voters not to "give in to fear" and vowed to step up security cooperation with EU partners.
On Wednesday, Macron will visit a household appliance factory in Amiens, northwest of Paris, that is threatened with closure, before holding a rally in Arras, a city in the northern rustbelt where the FN is strong.
Le Pen on Thursday will hold a night-time rally in the southern city of Nice -- another party bastion -- and next Monday will hold a traditional May 1 rally at a conference centre north of Paris.
The two are scheduled to meet in a TV debate on May 3.
