"Having spoken with our board it has been agreed that unfortunately we are not in a position to proceed with your inquiry and whilst I appreciate you are not asking for firm dates, we are not in a position to progress with the profile."
Mr Ross said it was "disappointing, if not extraordinary". "We suffered the same discrimination in the early years in Australia, but, as I have pointed out to you previously, all major venues now accept us as a major event, while we regularly attract crowds of 60,000," he wrote.
Ms Missina, a Sexpo tour guide who has been named "porn star of the year" for three years running, said the event was "not about objectification or exploitation".
"The big thing I find with people that haven't been to Sexpo is they get confronted with the sexual explicitness and they think it's basically an adult industry show full of sex workers and strippers and a glorified sex shop," she said.
"But it's so much more than that. Sexpo is a 50-50 split between entertainment and sexuality education. There are educational art exhibits, we run seminars with sexologists to talk about things like how to deal with jealousy in relationships."
Ms Missina said the event could be a life-changing event for attendees, particularly women. "It becomes a safe space for women to come and learn and express themselves," she said.
"I see women come in and they're covered up and a bit shy. At the end of the show these women are running around having a great time, coming out of their shell. Some go out and get their boobs covered in body paint and glitter, running around having the time of their life.
"I would say [to the UK] ... that mainstream media, everything has been so pornified, porn culture has infiltrated our music videos and ads and female sexuality is literally everywhere. Don't be put off by Sexpo being sexually explicit.
"It's about sexuality and how it can help you live your life, it's not about objectification or exploitation. Come to Sexpo with an open mind and see what it can do for you."
Sexpo hosts three shows a year in Australia and regularly attracts complaints from lobby groups including Collective Shout, which has called for a crackdown on its advertising appearing on public transport and billboards.
ExCel London has been contacted for comment.