Vittorio Sgarbi, an Italian junior culture minister and art critic currently under investigation for the possession of a stolen painting, announced his resignation on Friday. He cited the antitrust body in Rome attempting to limit his unofficial responsibilities as the reason for stepping down.

Sgarbi, 71, is a long-serving parliamentarian and outspoken TV personality who was close to former Primer Minister Silvio Berlusconi who died last year.

Sgarbi has been under pressure to resign for weeks over the painting scandal but said he was quitting "to avoid a conflict of interest" before beginning a lecture on Renaissance artist Michelangelo in Milan.

Sgarbi said the antitrust authority, which is investigating him over a possible conflict of interest, had informed him he should not attend an art conference.

He told his audience he had decided to preserve his freedom rather than respect its instructions.

"According to the antitrust notice, I should not talk about art, I should not deal with art. I should be a junior minister dealing with administrative duties, and limited ones," he said.

He attacked Culture Minister Gennaro Sangiuliano for not backing him over what Sgarbi said were "anonymous letters" to the ministry alleging he was accepting payments for non-ministerial duties, in a breach of regulations.

Prosecutors are investigating the politician, whose brief includes protecting the country's cultural heritage, over his ownership of a 17th-century painting that police say was stolen from a castle near Turin in 2013. He denies all wrongdoing.

On Monday, in a characteristic outburst, Sgarbi lashed out at two TV journalists interviewing him over the painting, saying he hoped they died and threatening to show his nude body.