Miss Great Britain, Zara Holland, has been stripped of her title after having sex on ITV2 reality show Love Island.
The organisation said it was with "deep regret" that she'd been "de-crowned".
Scenes showing the 20-year-old getting intimate with Vicky Pattison's ex Alex Bowen were aired on Wednesday.
"We pride ourselves on promoting the positivity of pageants in modern society and this includes the promotion of a strong, positive female role model in our winners," said a statement.
"The feedback we have received from pageant insiders and members of the general public is such that we cannot promote Zara as a positive role model moving forward.
"We wholly understand that everyone makes mistakes, but Zara, as an ambassador for Miss Great Britain, simply did not uphold the responsibility expected of the title."
She'll be replaced by runner-up Deone Robertson, who had been crowned Miss North Lanarkshire, and will now compete in the Miss World competition.
Zara said she regretted the decision in Thursday night's show.
She told the cameras: "You know when you're in the moment and it just happens. That's really not like me at all. Why couldn't we have just gone to sleep?"
The organisation said they would meet Zara on her return to the UK from the house in Majorca "to fully explain our decision and will wish her the very best going forward".
A spokesman for the show said a decision hadn't been made yet about when Zara would be informed.
Alex Bowen entered the Love Island house earlier this week with James Khan.
Zara was given the chance to go on a date with one of the two new men and chose Alex despite the fitness coach having spent the day flirting with fellow contestant Olivia Buckland.
The pair decided to spend the night together in the Hideaway and were then filmed having sex.
Love Island began in 2005, running for two series.
It was revived last year and is now hosted by Caroline Flack.
She wasn't happy with Miss GB's decision to strip her of her title.
2015's winners were glamour model Jessica Hayes and professional cricketer Max Morley.
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