The singer cancelled her appearance at the event on Saturday (September 1) after her team were said to be unsatisfied with the venue.
Pride Brighton and Hove said in a statement to Pink News: "The team at Pride Brighton & Hove are sad to announce that despite agreeing the full details of her performance in advance, Alexandra Burke and her management decided to remove her from the lineup at the last minute, disappointing thousands of her fans.
"[We] would like to thank Fatboy Slim, the Freemasons and all of the performers who waived their fees to perform at Preston Park for their support of Pride Brighton & Hove 2012 and the LGBT community at large."
Burke tweeted later that evening: "Hey Guys, due to circumstances out of my control I'm unable to perform at Brighton Pride today, so sorry guys."
Her PR representative Simon Jones of Hackford Jones added: "Alexandra Burke travelled to Brighton today for Pride, but due to technical & production issues on site, she was sadly unable to perform."
The star recently confessed that she gets upset when the press label her "a massive diva", adding: "I don't know where that came from but people make up horrible stuff - it comes with the job."
Watch the music video for Burke's 'Let It Go' below: