In the world of opera, it is rarely frowned upon if sopranos or tenors sport a few extra pounds. But before the curtain could go up in Rome on a production of Giuseppe Verdi’s La traviata, the scales appeared to have tipped the other way.

Daniela Dessi, an established Italian soprano, walked out of the production after its director, Franco Zeffirelli, had publicly abused her about her weight and age. She had been due to play the role of Violetta, a lithe courtesan who expires from consumption in the arms of her lover Alfredo.

“A woman of a certain age and plumpness is not credible in the character of Violetta,” the veteran film and opera director told her.

But while many top sopranos have been famously statuesque and long-lasting, Dessi is 52 and says that she weighs 65kg (10st 3lb), well within her operatic sell-by date and about half the size of some of the greats.

“Zeffirelli said these things and other, more offensive things,” said Dessi. “I believe a lot in the physical appearance of the singer. I have always taken care of myself. We should be respected for our voices. To be too thin is not good.”

Dessi, who is to star in Andrea Chenier by Umberto Giordano at the Teatro Real in Madrid next month, said other sopranos such as Monserrat Caballé — a woman of unashamedly generous proportions who had a hit with Freddie Mercury with the song Barcelona — had interpreted the role of Violetta without any comment about their physical appearance.

“You don’t sing with the body but with the voice,” said Dessi in an interview with the Spanish newspaper El Mundo. The singer, who has performed at some of the world’s most famous opera houses including Milan’s La Scala, has worked with Zeffirelli in the past. She said: “I respect the artistic past of Franco Zeffirelli, but I don’t have any admiration for the way he created this controversy.”

Fabio Armiliato, her husband, was due to sing the part of Alfredo in La traviata but also withdrew. Zeffirelli remained unrepentant yesterday. “I did say she was on the plump side for the part, and she is. She is is not exactly the kind of woman who is likely to die of tuberculosis,” he told The Times, arguing that La traviata was a story of “youth and sensual passion”. He said he had offered Dessi an alternative part as Alice Ford, a “mature woman” in Verdi’s Falstaff, but she had turned it down.

Dessi is consulting her lawyers about possible legal action against Zeffirelli, 86, who has enjoyed a long and distinguished career as a director of both operas and films, including his 1967 debut The Taming of the Shrew starring Elizabeth Taylor and Richard Burton, Romeo and Juliet in 1968, and Jesus of Nazareth in 1977 which became an ITV television mini-series.

Asked about the threat of legal action, he said: “She can threaten what she likes, but I am entitled to choose my singers and exercise my artistic freedom.”

Gianluigi Gelmetti, the chief conductor of the Rome Opera — who is believed to have hired Dessi for the role — disagreed with Zeffirelli’s assessment of the performer, saying Dessi’s voice was “in excellent form — and I have to say that her appearance pleases me as a man”.

Opera singers are no strangers to gibes about weight. In 2004 the American soprano Deborah Voigt was sacked from the Royal Opera House’s production of Richard Strauss’s Ariadne auf Naxos because she was thought to be too fat. It was said at the time that it was felt she would not suit her costume. Voigt later had gastric bypass surgery to reduce her weight.

Luciano Pavarotti, who died in 2007, was said to have suffered increasingly poor health, partly because of his fluctuating weight. It has often been said that rounder figures make for better voices in the rarefied world of opera. When Maria Callas shed more than 20 kilograms towards the end of her career, critics claimed her voice was never the same again.

Some opera singers also say that if one is out of shape, a night on the stage can be a struggle. The British bass Sir John Tomlinson said: “To get through a long night of Wagner you have to be fit. It’s like running a marathon.”

As for her age, Dessi, while perhaps no dead ringer for Violetta, is well within the average career limit for a recognised opera singer. The Australian soprano Joan Sutherland sang Violetta aged 53 in a classic 1979 Decca recording with Carlo Bergonzi.

Zeffirelli is still a dominant force in Italian opera. Last September a decision by New York’s Metropolitan Opera to open its 2009-2010 season with a new production of Tosca directed by Luc Bondy caused a stir after a number of opera fans demanded Zeffirelli’s 25-year-old staging instead.

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