An Italian art critic who was recently placed under investigation over allegations that a 17th-century painting in his possession was stolen from a castle more than a decade ago has resigned as a junior culture minister.

“I am resigning with immediate effect as undersecretary of the government and will inform [the prime minister, Giorgia] Meloni in the next few hours,” Vittorio Sgarbi said on the sidelines of a conference in Milan.

Sgarbi, 71, who denies the allegations over the painting, is also being investigated by Italy’s antitrust authority for allegedly accepting lucrative fees for appearing at cultural events.

Il Fatto Quotidiano newspaper calculated that the deputy minister had received about €300,000 in nine months for appearances.

Sgarbi did not mention the case of the stolen painting on Friday. Instead he referenced the antitrust investigation that was launched in October.

“I’ve done occasionally – occasions can also be daily – conferences like this [the Milan event],” he said. “This conference, according to what the antitrust authority has sent me, would be incompatible, illicit, outlawed. Therefore, in order to prevent all of you from being accomplices to a crime, I speak from this moment free from my mandate as undersecretary.”

Sgarbi had been due to face a vote of no confidence scheduled for 15 February and is the first person to resign from Meloni’s far-right government. He has drawn criticism in the past for using profanity and making sexist comments during public appearances.

In early January prosecutors said they were investigating Sgarbi for the alleged laundering of stolen art after claims broadcast on Report, an investigative series on the public broadcaster Rai.

Margherita Buzio, the owner of La Cattura di San Pietro (The Capture of Saint Peter), a painting by the artist Rutilio Manetti, reported the work stolen from her castle in Piedmont in 2013, telling police at the time that the canvas had been cut from its frame.

A person identified by Report as a friend of Sgarbi’s is alleged to have visited the castle a few weeks earlier to inquire about buying the painting.

The work, which was damaged during the theft, was entrusted to an art restorer for repair a few months later, according to the allegations. The restorer told Report that the work he was given was the stolen painting.

In 2019 the painting is said to have been transferred to another restorer, by which time a candle had been added to the top left corner, allegedly to make it less identifiable. It is unclear who put the candle there.

Sgarbi has said a painting he presented at an exhibition in Lucca in 2021 was the original version of The Capture of Saint Peter, which he said he found while restoring an abandoned villa bought by his mother in Viterbo in 2000. He said the painting stolen from the castle was a “bad copy” produced in the 19th century.

Sgarbi told the newspaper Corriere della Sera last month that those claiming he modified the painting were “ignorant”. “Manetti’s style was just that – he put candles everywhere,” he said. “My painting is the original, the other is a badly made copy.”

A video of Sgarbi surfaced this week in which he is seen yelling and swearing at a journalist, saying: “If you die in a traffic accident, I’ll be happy.” He apologised for the comments on Friday.