Bulgarian ultranationalist MP Volen Siderov’s immunity from prosecution has been challenged by the country’s Chief Prosecutor.

The move follows the latest scandal stirred by the leader of the extremist Ataka (Attack) party.

Late on Monday, Siderov verbally assaulted a French cultural attach? during a Sofia-Varna flight and later attacked a passenger and a police officer in a Varna airport shuttle bus. He is now investigated for hooliganism and causing slight bodily harm.

Chief Prosecutor Sotir Tsatsarov demanded on Wednesday that the ultranationalist be stripped of his immunity as lawmaker, noting that his behavior was “extremely scandalous and cynical."

Tsatsarov has sent a request to lift Siderov's immunity to Parliament Speaker Mihail Mikov.

Varna district prosecutors have gathered evidence showing that Siderov “committed indecent actions, grossly violating the public order and showing a clear lack of respect for society.”

Prosecutors have further noted that he caused a slight bodily harm to Varna police officer Kostadin Kolev who was on duty at the time of the incident.

Meanwhile, Siderov gathered a rally of some 50 supporters in Sofia on Wednesday, claiming that the latest airport incident was the result of a conspiracy plot against him organized by famed US investor George Soros.

Volen Siderov, the leader of the ultranationalist Ataka  party, has been involved in a number of scandals over the last few years. In 2010, he was detained in Germany after he hurled racist insults at the attendants of a Lufthansa flight.

In September, he and a group of Ataka MPs stirred a row in a renowned Brussels restaurant.

Earlier last year, he was spotted carrying a gun to the Bulgarian Parliament.

In 2011, he led an attack on praying Muslims in front of a Sofia mosque.

Even though it is not officially in power, Siderov’s anti-Western party remains a key ally of the country’s fragile Socialist-led coalition government.