Connie's theatre is alive with the Sound of... Karaoke

When she won her starring role before a TV audience of millions in the BBC show How Do You Solve a Problem Like Maria? the 23-year-old singer insisted she would be able to perform the maximum eight shows a week.

Six months later, and after frequent absences due to illness, she is a little sadder, wiser - and quieter.

Having just returned to the stage after two weeks off with damaged vocal cords, her performance is being boosted with a recording of her voice.

A so-called "click track" - a digitally enhanced recording of music and lyrics - is being used during songs such as The Lonely Goatherd and I Have Confidence to ensure the high notes are reached.

A theatre source claimed Miss Fisher was now "just miming" some of the songs. But a spokesman for the show was adamant the backing track was simply boosting her voice and that she was still singing.

Since taking up her role in Andrew Lloyd Webber's musical version of the 1965 movie, Miss Fisher has had to miss 32 of the 83 performances at the London Palladium.

The theatre insider said she had been battling vocal cord problems for some time.

"It has affected her for the past six weeks and is effectively a bleed on the vocal cords. There is a risk it could start again. Friday was the first time that a click track was used in the show. The musical director very discreetly put in an earpiece for those two tracks and it was clear they didn't want the audience to know.

"Worse still, they did not tell the children in the show what was happening and it was all out of time.

"It sounded like they had taken her voice from the CD track but as the show song is a lot faster, it was a bit of a shambles.

£I Have Confidence, in particular, is quite a physical song but there was absolutely no change in tone. Whereas singing live her breathing patterns would have been different, which made it more obvious.

"I don't know if the audience realised but to everyone else it seemed to be glaringly obvious.

"If people are paying £50 plus for a ticket, they don't want to just listen to a CD of someone's voice."

A spokesman for the show played down the use of a click track, saying: "It's common practice. It's used in shows and not particularly peculiar. It does not completely replace her voice.

"She is still singing. The click track simply augments her sound for the audience."

The claims come days after the Mail revealed producers were cutting Miss Fisher's eight performances a week to six.

Aoife Mulholland, one of the TV finalists Miss Fisher beat to win the role of Maria, will appear twice a week from April. She is currently playing Roxie Hart in Chicago.

Andrew Lloyd Webber recently blamed himself for Miss Fisher's problems.

"Connie was so determined to prove she was the people's Maria that she insisted on all eight (performances). But we should have insisted that she do the six, and we didn't," he said.