Three gay men from Wales are suing Pizza Hut for sexual discrimination after they were refused service at a restaurant in Blackpool.
Pizza Hut said it was taking the allegation "extremely seriously"
Michael Kemp, 42, Paul Barnabas, 47, and his partner Iain Buck, 38, were among nine gay men and transsexuals who visited the Church Street restaurant.
The group, some of whom were in women's clothes, were told to go elsewhere as the venue had run out of pizzas.
Pizza Hut said it was taking the allegation "extremely seriously".
The incident, which happened last July, followed a ruling made three months before which made it illegal for retailers and catering establishments to refuse to serve customers on the grounds of their sexual orientation, religions or beliefs.
However, at the moment the law does not incorporate transsexuals.
The Equality and Human Rights Commission is considering representing the case but a decision will not be made until the end of the month.
Mr Kemp is a member of Encompass, a group for gay, lesbian, bisexual and transsexual people in Flintshire.
A spokesman for the organisation said: "The law is quite clear. It is now illegal for shops, bars or restaurants to refuse to serve anyone because of their sexual orientation.
"This group of people simply wanted to sit down and enjoy a pizza like anyone else, but instead were subjected to humiliation and told to go elsewhere.
"Quite rightly, they have now put in a claim of discrimination because of their sexual orientation."
A spokesperson for Pizza Hut said: "We find discrimination of any kind completely unacceptable and are taking this allegation extremely seriously.
"Unfortunately, we are unable to comment further as this matter has been passed to our solicitors."