The French presidency is to fire a top security aide who beat a protester during a demonstration in Paris in May after saying “new facts” had emerged in a scandal that has deeply embarrassed Emmanuel Macron.

A video released this week shows Alexandre Benalla, 26, dragging and hitting a demonstrator while wearing a police helmet and armband, even though he is not a member of the force.

Paris prosecutors also said Mr Benalla has been detained for questioning in the assault inquiry, where he also faces charges of impersonating a police officer.

A second reservist gendarme, Vincent Crase, also present on May 1, has also been detained for questioning.

Prosecutors have also quizzed "as a witness" Mr Macron's principal private secretary, Patrick Strzoda, who told Le Monde that he had granted Mr Benalla authorisation to accompany police to the May Day protest as an "observer".

"New facts that could constitute misdemeanour by Alexandre Benalla were brought to the president's attention," said an Elysée official. "As a result... the presidency has decided to start Alexandre Benalla's dismissal procedure," the official added.