When two opera singers have a difference of opinion, a genteel spat over the interpretation of a Puccini aria or suitability for a role in La Bohème might once have been expected.

But in the lucrative and crowded world of "light-classical" it seems that cleavage is the burning issue for stars vying for top spots in the easy-listening charts.

The latest front in the opera wars was opened yesterday when Marina Laslo, a Russian singer whose rendition of Ave Maria has made her one of Classic FM's most played artists, objected to a record company executive's suggestion that she needed to "sex up" her image.

Laslo, 24, said: "I was raised to conduct myself like a lady and have no interest in compromising those standards to achieve a short-cut to fame. The market is full of blonde classical artists with their cleavages on show."

The last phrase, made after an abortive meeting with one several labels vying for her signature, was seen yesterday as a dig at the Welsh singer Katherine Jenkins and other female acts such as the Opera Babes and Charlotte Church.

Jenkins, 25, who recently returned from entertaining British troops in Iraq, has enjoyed a stellar rise to fame since being talent-spotted in 2003, teaching singing in a Hertfordshire comprehensive.

The mezzo-soprano from Neath has sold more than 1.5 million records in Britain in the last 18 months after securing a £1m six-album deal with the label Universal Classics.

From Vanessa Mae to Mylene Klass, record companies have been increasingly anxious to cash in on their young female classical performers. Promotional shots of Jenkins, who last year won a Classical Brit for her second album, normally display her in evening gowns and have not been afraid to show a hint of cleavage.

But the singer has claimed that despite her glamorous image, she is aware of the need to appear demure to her core audience.

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In a recent interview she said: "I like to be glamorous when I'm working - I've always been a girlie girl ... But I hope I keep my look classy - I don't like to show everything off at once. I like to be more sophisticated."

The rise of classically-trained singers such as Jenkins and the Opera Babes, Rebecca Knight and Karen England, who were discovered busking in London's Covent Garden, is part of the lucrative "cross-over" market between pop and classical music.

The all-woman quartet Bond have helped record companies to buck the trend of declining classical music sales. Classical album sales in Britain have increased by 8 per cent compared to 2002, making the market worth £65m.

Industry insiders pointed out that all performers in the sector, including Laslo, hitherto best known to the British public as the some-time girlfriend of the chef Jean-Christophe Novelli, have made sex appeal part of their selling point.

One London-based agent said: "The truth is that in this market sexiness is part of the deal. The idea of a classically-trained siren is always going to be more alluring than a middle-aged maestro. I've seen Marina's promotional shots and physical attraction is part of what she does."

The trend has angered major figures in British classical music. Sir Thomas Allen, the leading baritone, said: "Sugar-coated programming, or the recording of choice bits of easy listening, is a plague and has taken over a once respectable and serious profession. I don't want Janet Reger rip-off attired Gregorian babes and the idea of a wet T-shirted quartet where once was the Amadeus [String Quartet] has me reaching for the seasick pills."

A spokeswoman for Laslo said: "Marina was not talking about anyone in particular. She is a passionate woman and occasionally she says what she feels."