Alexandre Benalla, the security official who sparked the biggest scandal of Emmanuel Macron’s presidency when he was filmed illegally dressed as a police officer beating people on the edge of a demonstration, has told the French senate he wasn’t the president’s official bodyguard but was allowed to carry a handgun because he was concerned for his own safety.

Benalla, a civilian adviser who was close to Macron, sparked a major political scandal this summer when video footage emerged of him illegally dressed as a police officer, beating and kicking two people on the edge of a May Day protest in Paris.

The scandal grew when it emerged that Macron’s office at the Élysée Palace had been informed of Benalla’s misconduct at the time but had not reported him to the police and, after making him take time off work, had allowed him to continue at the presidential palace in a different role.

The 27-year-old has been charged with assault and impersonating a police officer and is under police investigation.

But the French senate has taken the rare move of launching its own separate inquiry into the workings of the presidential palace under Macron, attempting to determine whether Benalla enjoyed special favours and whether he was part of a parallel security operation for the president, despite not being a police officer.

The senate is examining how Benalla, who was head of Macron’s security team during the 2017 presidential campaign, was subsequently given a well-paid job in the presidential palace, why he appeared to have privileges, including being allowed to carry a firearm when the president’s protection should have been the preserve of a special police unit.

Benalla, who has often been seen flanking Macron during public outings as president, denied that he had ever acted as his bodyguard – a job reserved for elite members of the gendarmerie.

“I was never a police officer nor the president’s bodyguard,” Benalla said. He added that his role was more like that of theatre “director” or orchestra “conductor”, organising Macron’s presidential trips and personal outings and putting events into place. He said he also dealt with diplomatic gifts for foreign travel.

Benalla, a fan of the film In the Line of Fire about a US secret service agent trying to thwart a presidential assassination plot, was asked repeatedly about how he came to be authorised to carry a gun. He said he had a gun “for his own personal security” and that it was sometimes the case that he carried his Glock 43 handgun while on outings with Macron.

“I would arrive in the morning with the gun on my belt and leave in the evening with the gun on my belt,” he said, insisting he carried the weapon for his personal safety but not detailing why.

He also admitted to securing an exclusive badge granting him access to the National Assembly parliament building on a “personal whim”, so he could use the parliament’s gym and library.

Senators were not authorised to question Benalla over the incident where he was filmed beating people on the edge of the Paris demonstration, but they insisted they were concerned about due process in Benalla’s hiring and actions at the Élysée. “What we are interested in is the functioning of the state,” the Socialist senator Jean-Pierre Sueur said.

Police unions said Benalla’s testimony to the senate was ambiguous and left questions unanswered about why he was allowed to carry a firearm.

The scandal is damaging for Macron, who beat the far-right Marine Le Pen to win the presidency last year and pledged to restore transparency and integrity to the nation’s highest office.

Macron, whose poll ratings have dropped since the summer, has acknowledged Benalla’s failings were “serious” but has also dismissed the scandal as “a storm in a tea-cup”, saying the Benalla incident was being used to attack him.

Lawmakers for Macron’s centrist party, La République En Marche, have boycotted the senate hearing, accusing the opposition-dominated upper house of parliament of mounting a deliberate ploy to seek to damage the president.