Jessica Mauboy has revealed the reason behind her absence on the stage at the Melbourne Cup after days of silence.

The singer was scheduled to perform the Australian national anthem before the main race on Tuesday, but failed to show at the last minute.

There were rumours non-compliant shoes were to blame and, although it seems they were part of the problem, Mauboy claimed there was a more serious explanation for her no-show.

Mauboy told News Corp a disagreement between her team and the Victorian Racing Club, possibly over shoes that did not conform with exclusive sponsorship rights, led to a panic attack.

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“Four minutes before I am about to be walked out from the green room, people on one side are bickering with people on another side and it started to suffocate me, it was crazy and I didn’t know what to do,” she said.

Mauboy described the attack – the first she had ever experienced – as “the scariest moment ever”.

She posted a message thanking fans for their support to social media on Wednesday.

“I was really looking forward to it and of all the days for things to go wrong, unfortunately this was the one,” she wrote.

“I am so sorry to everyone for the disappointment.”

Mauboy performed the national anthem to a massive crowd at the NRL grand final in October, which followed other high profile performances at Eurovision and in front of US President Barack Obama.

But she said although she was prepared for the “big gig”, she could not refocus before going onstage.

“I should have been prepared to just walk on stage and do my job, the job I love and they didn’t allow me to do that,” she told The Daily Telegraph.

Mauboy was also currently promoting a new fragrance, Be Beautiful, as well as a new music single and TV series.

She was not the only one who reportedly fell foul to exclusive sponsorship rights.

US actress Hilary Swank was unable to be pictured with the Melbourne Cup as she was wearing a dress exclusively stocked by David Jones – a major competitor to the Cup’s sponsor, Myer.