Anti-corruption investigators have raided the home and party headquarters of Jean-Luc Mélenchon, prompting a furious – and potentially illegal – protest from the leader of France’s hard left.

The raids – part of twin inquiries into the alleged misuse of European parliament funds and suspected funding irregularities in Mélenchon’s presidential campaign last year – took place on Tuesday at the offices of his party, France Unbowed, and private apartment.

In video shot by reporters at the scene, Mélenchon, 67, railed aggressively at a police officer standing in front of the door to the party’s offices in the rue de Dunkerque, near the Gare du Nord, repeatedly demanding he not be touched.

Quotidien (@Qofficiel) [#Thread]

Après la #perquisition menée à son domicile, Jean-Luc Mélenchon s’est rendu au siège de la France insoumise, également perquisitionné.



Voici la scène hallucinante devant la porte de son propre local. ⬇#Quotidien pic.twitter.com/c661VAxp5q

“We are not thugs, we are not bandits,” he shouted. “In whose name are you preventing me from entering my party’s office? Go away and do your work as republican police officers. I am the republic; I am an MP.”

The far-left leader continued: “Are you not ashamed? You are the police of the republic, or you are a gang? Do you know who you are talking to? You know who I am? Do I represent nothing to you?”

As the officer refused to budge, Mélenchon urged parliamentary colleagues and party staff who had accompanied him – several of whom wore the red-white-and-blue sash of members of the French national assembly: “Kick down the doors, comrades!”

Facebook Twitter Pinterest Jean-Luc Mélenchon speaking to the press after the police search at his party headquarters on Tuesday. Photograph: Christophe Petit Tesson/EPA

The group subsequently entered the offices by another door and objected forcefully to the investigators’ presence, prompting them to leave before the search was completed, according to a reporter from the Liberation newspaper who was at the scene.

Later, standing outside, Mélenchon called the raids an “enormous operation by a politicised police force”, adding in a video posted on his Facebook page that the searches were “a politically motivated act, an act of political aggression”.

He was not afraid of anyone, he added: “These people can invade my house, my party headquarters and my movement, but they will not scare me. We haven’t stolen anything. We are honest.”

A source close to the raids, which targeted 15 separate addresses and included another leftwing party, said they were carried out by a specialist anti-corruption unit that focuses on financial and tax irregularities.

Several French parties, including Marine Le Pen’s far-right National Rally (formerly the Front National) and the centrist Modem party, are being investigated over their alleged use of European parliament funds to pay party staff in France.

The French prime minister, Édouard Philippe, said in parliament that he “understood the emotion and anger” of the far-left leader, but that the justice system was “completely independent” and the public prosecutor had acted entirely of her own accord in ordering the raids.

A justice ministry spokesman said it was “completely unacceptable” to prevent investigators from carrying out their work. France’s penal code allows for a penalty of up to six months’ imprisonment for attempting to discredit the judiciary or challenge its authority or independence.