Toni Servillo, star of Oscar-winner ‘The Great Beauty’, on ‘Inner Voices’ at the Barbican

“Thank you Italy!” said the visibly surprised director Paolo Sorrentino on receiving the Golden Globe for best foreign film for his artful masterpiece The Great Beauty last month. “It’s a truly strange country but a beautiful one.” If you detect any ambivalence towards his native country, you wouldn’t be wrong. The luscious images in Sorrentino’s lauded film are both a celebration and a savage critique of a nation that appears to have mislaid its moral compass.

At the centre of the rottenness is the jaded cultural journalist Jep Gambardella, played with a consummate mix of ennui and sentimentalism by Toni Servillo. The actor’s deadpan expressions, strategically raised eyebrows and withering cynicism are a lucid counterpoint to the beauty all around him. He knows it is false, or at least premised on false values, but he can’t get enough of it. This is la dolce vita as addiction, its pimps, posers and parties dragging a once-great creative culture into a dark place.

Servillo has been here before. The 54-year-old actor’s collaborations with Sorrentino have resulted in some of the greatest Italian films of the past decade: from the director’s breakthrough, The Consequences of Love (2004), to Il Divo (2008), his coruscating account of the life of former premier Giulio Andreotti. Add to that Servillo’s performance as a crime boss in Matteo Garrone’s highly acclaimed Gomorrah (2008), and you have a mighty trilogy of state-of-the-nation indictments.

The Great Beauty has also been nominated for best foreign film in this weekend’s Oscars but Servillo is unsure if he can afford the time to zip to Los Angeles for the ceremony. He is embroiled in more serious matters: a worldwide tour of Inner Voices, a work by the Neapolitan playwright Eduardo De Filippo, in which he plays the lead, in addition to directing.

Inner Voices, which arrives at London’s Barbican Theatre on March 26, is also a work with a conscience. Servillo, himself born in the province of Naples, plays the Neapolitan Alberto Saporito, who suddenly accuses the family next door of having taken part in a murder. He later realises the vision was only a dream but it is too late to stop the neighbourhood reverberations, with tragicomic results.

“It is a cry of alarm,” Servillo tells me, barely half an hour after receiving a standing ovation for his performance in Paris’s MC93 Theatre in Bobigny, Paris. “The play was written in the shadows of the ruins that were caused by the second world war, which destroyed the country. But Eduardo looked at the horizon and saw moral ruins ahead. And today we can see those moral ruins.

“And despite the tragedies that have befallen Italy in recent years – the bribery scandals, the abduction and killing of [politician] Aldo Moro, the trials of leaders accused of complicity with organised crime, the Mafia slaughters – Italy has still not succeeded in pulling back from this moral precipice. Enrico Berlinguer [leader of the Italian Communist party] used to say it but nobody listened to him: the Italian ‘question’ is a moral question.

“The most interesting theme to emerge from this play is how the legitimisation of criminality has today become an indecent habit. It is seen as something positive. So for these reasons, Eduardo’s appeal to our individual consciences is still absolutely relevant.”

I ask if the worldwide tour, which has already taken in Chicago, and is due to make a stop in Madrid after London, has a promotional element, making more people aware of the playwright’s works. “He is the Italian Molière,” Servillo says with enthusiasm. “Taking into account their different eras, of course, both were real men of the theatre, who wove together their own lives and what was happening on stage. They were both writers, directors and great actors.”

De Filippo’s talents, he says, lay in his eclectic tone, pitched somewhere between Pirandello and Beckett. “He could bring together great simplicity and also complication; superficiality and depth. He was the last playwright in Italy who could combine that nobility with great popularity.”

I ask why that tradition died. “Because the theatre in Italy has lost its ritualistic importance,” Servillo says. “Eduardo’s works are the last examples where people could come to the theatre, and see themselves in a mirror. They could find themselves in the theatre.

“After that, things changed. Take someone like Pasolini, who wrote for the theatre – but it was very literary, very intellectual. Eduardo was a writer who wrote for the audience, there was none of that intellectual narcissism, just a real joy in communicating, as you find in Mozart.”

Servillo has also directed opera, and I ask if such a mannered art form can give him insight into the rest of his work. “Yes! I do it with great pleasure. Opera is musical theatre, and the music can teach you so much about the theatre. Very often I use musical terms to think about how I comport myself on stage: I employ rubati, ostinati, cadenze. Finding these parallels is very fascinating for me.

“But I am against the setting of opera amid the simulacra of modernity. I saw an Ariadne auf Naxos which had Bacchus on a skateboard, and Zerbinetta as a drug addict. With respect, that is not the tradition I belong to.”

How does he reconcile his understated cinematic performances with the expansive style demanded by the theatre of De Filippo, and which does he prefer? “I always answer the same way as the great French actor Louis Jouvet: to ask if an actor prefers theatre or cinema is like asking a fish if it prefers the sea or a chlorinated swimming pool.”

I wish Servillo luck on Oscar night, and ask if The Great Beauty is not yet another devastating account of contemporary Italian life.

“In a way, yes,” he says. “For me the most interesting metaphor is that of Jep, who is a man who is wasting his talents away. He has lived through this long line of lost opportunities, and all he has left is the beauty of the past. And this is how our country is, neurotically focused on today, because it does not know how to regard its past, and cannot see the future.”

The film has been widely seen as an updating of Fellini’s masterly portrayals of decadence from the 1960s and 1970s. “Yes, but the difference with [the films of] Fellini is that, back then, you could see a future. It is two different Italys.”

‘Inner Voices’, Barbican, London, March 26-29, supported by Eni, barbican.org.uk