Alexandre Benalla sat down for a long interview with French daily Le Monde, one week after the paper broke the story of his violent altercations with Paris May Day protesters while wearing a police helmet and armband.
"I feel like I have done something really stupid. And have made a mistake... I should never have gone to that demonstration as an observer, I should have held back," he told the newspaper.
But Benalla also denounced what he said was a "desire to get at the president" over the scandal.
'If I wasn't a presidential aide, I would do it again'
The former Elysee aide said he was angered by the sight of May Day protesters throwing bottles and other projectiles at police at the Place Contrescarpe in Paris.
"What's going through my head is, 'if we stand here doing nothing, we'll be isolated...we can't let these delinquents get away with this,'" he said. "Throwing projectiles at police, that's voluntary violence, it's a crime punishable by prison, that's what I was thinking."
According to him, his mistake was acting instinctively on his anger. "I'm at fault for letting myself go. And for forgetting my presidential duties. That's what I was later punished for. It wasn't because I committed a crime, it's because I made a political mistake that hurt my image."
Benalla defended his actions by citing article 73 of the penal code, which states that citizens have the right to apprehend someone in the process of committing a crime.
He said that his "engaged nature" made it difficult for him to watch protesters "as they destroyed with impunity."
"If I wasn't a presidential aide, I would do it again," he said. "But as a presidential aide, I wouldn't do it again."
'I understand the disappointment'
The 26-year-old said he "understood" Macron's Tuesday statement in which the president said he felt "disappointed and betrayed" by Benalla's actions.
"I don't see what other terms he could have used, given the scandal that's erupted," he told Le Monde.
"Presidential collaborators shouldn't be causing problems for the president."
Macron came out of his week-long silence regarding the affair on Tuesday, when he accepted responsibility at an event hosted by his Republic on the Move (LREM) party in Paris.
Opposition cries foul
The opposition Republicans party are set to file a vote of confidence in the government on Friday -- a largely symbolic move, since Macron's LREM holds a strong majority in parliament.
Two parliamentary committees have been grilling Macron's top aides along with police and military figures over the affair, with the president's chief of staff Alexis Kohler the latest to take the stand on Thursday.
Kohler, speaking before a Senate committee, acknowledged that officials' initial decision to punish Benalla with a two-week suspicion may "appear insufficient" but at the time it seemed "proportionate".
Revelations that top officials in Macron's office knew about the incident, but did not report it to prosecutors, have sparked furious opposition claims of a cover-up in the worst scandal to hit the Elysee since the 40-year-old office took office last year.
Prosecutors launched a probe after Le Monde published the video last week.
Benalla was charged Sunday with assault and impersonating a police officer, and was sacked Friday by the Elysee.