According to the Daily Mail, 53-year-old Emma Czikai said that she felt "degraded" following the negative feedback she received from judges Cowell and Amanda Holden.
After her audition, Cowell told her: "Emma, Emma, reality check here, it's not the music; it's not the microphone; it's you."
Czikai argued that her performance was affected by her medical conditions and is now suing Cowell's company Simco Limited on the basis of 'disability discrimination'.
At a pre-tribunal review today in London, she said: "I am certainly not prepared to be humiliated.
"Because I have these illnesses, singing is all I can do for my future and therefore it is important for me not to have 13 to 20 million people all over the world thinking I cannot sing.
"It is quite upsetting to be regarded as a failure and to be targeted and mocked.
"It was the microphone. It was the music. I have not got a horrible singing voice when I am in a fair environment that meets my disabilities as I proved on Britain's Got More Talent."
A representative for Simco Limited, Thomas Linden QC, said that it was opposing Czikai's right to have a full hearing on the basis that Britain's Got Talent is not an employer and cannot be treated as one.
Judge for yourself