At a gathering of lawmakers from his Republic on the Move party (LREM), Macron said he was "in charge" and considered the actions of his now-fired aide Alexandre Benalla a "betrayal."
"If they are looking for the person in charge, the only person, it's me and me alone," Macron said, according to lawmakers present at the event marking the end of the parliamentary session.
"I am the one who trusted Alexandre Benalla," Macron told them, adding that the 26-year-old former bodyguard had been a supporter during his campaign but that he felt like "the acts on 1 May were a disappointment or a betrayal."
Benalla was dismissed last Friday after videos emerged of him hitting a young man and wrestling a woman to the ground during May Day protests in Paris, while wearing a riot officer's helmet and police armband.
Benalla had been given a two-week suspension without pay days after the incident in May, and removed from organising the president's security during his trips.
But the alleged assault was not reported to prosecutors, who opened a probe after French daily Le Monde published the video last week.
The scandal, dubbed "Benallagate", has prompted opposition claims of an attempted cover-up, which the government denies.
Majority pleased, opposition unsatisfied
The LREM majority has hailed Macron's Tuesday statement taking responsibility.
"The president accepts all responsibility and refuses to cast the blame on someone else," LREM MP Aurore Bergé wrote in a tweet, adding that he'd faced down "public anger" and held off on "the temptation to get rid of others" or "answer the call for heads to roll."
Contre l'émotion de l'instant, contre la tentation de se défausser sur d'autres ou cet appel à "faire tomber des têtes", le président prend toutes ses responsabilités et réfute "la République des fusibles."Aurore Bergé (@auroreberge) 24 juillet 2018
"Le seul responsable, c'est moi. Qu'ils viennent me chercher." pic.twitter.com/3Nos78ftbu
But many in the opposition criticised Macron for making his announcement at an event hosted and attended by his own party, instead of addressing all of parliament or the country at large.
Conservative MP Eric Ciotti of the Republicans party tweeted: "Macron confirms what we've been saying since the beginning, that he's responsible for the state scandal that is the Benalla affair. But he prefers to explain himself to his exclusive inner circle rather than to the French people."
#Macron confirme ce que nous disons depuis le début et admet qu’il est responsable dans le scandale d’État de l’affaire #Benalla. Il préfère s’expliquer dans l’entre-soi de sa petite caste plutôt que de donner les explications qu’attendent les Français #MacronBenallaEric Ciotti (@ECiotti) 24 juillet 2018
Christian Jacob, also of the conservative Republicans party, has announced he will seek a no-confidence vote against the government, though this would be unlikely to succeed given the solid majority held by Macron's LREM party.
The opposition has seized upon the scandal, which has paralysed parliamentary debate as committees in both the National Assembly and Senate hold investigative hearings.
Parliamentary hearings continue
Several cabinet members and security chiefs are set to appear before Senate panels Wednesday, including Colonel Lionel Lavergne, the head of presidential security, and Eric Morvan, the director general of French national police.
Patrick Strzoda will also appear before the Senate, one day after being questioned in the Assembly.
Strzoda told MPs Tuesday that he decided there weren't enough elements to justify turning Benalla over to prosecutors, not least because no criminal complaint had been filed against him.
Macron's chief of staff Alexis Kohler will appear before the Senate committee on Thursday.
Benalla deflects blame
Benalla has defended his intervention during traditional May Day demonstrations in the capital, which were marred by clashes between police and around hundreds of youths.
In a statement from his lawyers, he said the young man and woman he was filmed scuffling with were "particularly violent individuals" he had been trying to "bring under control" while "lending a hand" to police.
Along with Benalla, Vincent Crase, a security agent employed by Macron's party who was also at the scene, has been charged with assault.
Macron's ratings take a plunge
Earlier on Tuesday, before Macron's statement accepting responsibility for the Benalla scandal, an Ipsos opinion poll found that 60 percent of French people reported an unfavourable opinion of the president a record low for the 40-year-old centrist.
An Elabe poll found 80 percent were "shocked" by the scandal, with 75 percent urging Macron to break his silence.
It took Macron nearly a week to comment on the affair since the Benalla video was published by Le Monde on 18 July.
*This article was updated with the names of two figures appearing before the Senate for questioning on 25 July: Colonel Lionel Lavergne, the head of presidential security, and Eric Morvan, the director general of French national police.