At least eight professional footballers have revealed to colleagues that they are gay, but have refused to go public because they fear a backlash from fans.

This latest evidence that British football remains a homophobic environment comes after Jason Collins, a high-profile American basketball star, became the first player from a US professional sports league to reveal that he was gay.

In Britain, no professional footballer has come out and continued his career since Justin Fashanu in 1990. He stopped playing in 1994, but hanged himself four years later, aged 37. Fashanu had said that he had not been prepared for the backlash that followed his disclosure, and that his football career suffered "heavy damage" as a consequence.

In January, Robbie Rogers, an American playing for Leeds United, left the club by "mutual consent". A month later he announced he was gay. In a statement, Rogers, 25, said that remaining in football after declaring that you were gay was "impossible". Last week it emerged that he had left England and was training with the Los Angeles Galaxy football team in the US.

Gay campaigners told the Observer that Clarke Carlisle, chairman of the Professional Footballers' Association, had revealed that eight players had approached him to disclose that they were gay. Seven told him that the reason they would not reveal their sexual orientation publicly was not the reaction from the dressing room or club, but the potential reaction from the media and supporters. Chris Basiurski, chair of the Gay Football Supporters' Network, said that, although progressive attitudes had begun to infiltrate the dressing room, the fear of how supporters would react remained a problem.

"The danger is not so much coming out, but what happens next," he said. "One of the problems Justin Fashanu found was that he was the first black millionaire player, and a lot of things were expected of him on the pitch at Nottingham Forest and it didn't really work out. When that happened, the dressing room and the management used his sexuality as a thing to bash him with."

Basiurski said the organisation had heard reports of professional players whose sexuality was a secret guarded inside the game: "We have anecdotal evidence that players are out within their clubs and don't have a problem. But we are trying to create an atmosphere for people to come out safely, but at the moment there is a big barrier. The fact is, we have never really tested the fans, both home or away, on this.

"The danger is what happens when a player comes out and gets loads of support and attention, but then start playing badly. The worry is that fans will start getting on their backs and they may lose the confidence of their manager and it could be connected to their sexuality."

Last month fans of Brighton & Hove Albion called on the football authorities to increase efforts to tackle homophobic abuse after a report showing that it was prevalent in 72% of the club's games this season. Brighton has the popular reputation of being Britain's gay capital. The findings, which include allegations of chanting, gestures by players and threats made to supporters, were compiled by the Brighton & Hove Albion Supporters' Club. The issue of homophobia within football is gradually gaining political momentum, with Yvette Cooper, the shadow home secretary, describing the absence of openly gay professional footballers in the UK as "outrageous", while two weeks ago MPs tabled a parliamentary debate calling on clubs, supporters and football authorities to eradicate homophobic chanting.

Stonewall, the gay charity, has conducted research finding that 60% of supporters believe that anti-gay abuse from fans dissuades players from coming out. The organisation is working closely with the FA and PFA as part of the Kick it Out campaign to rid the game of homophobia. Andrew Wasley of Stonewall said: "There are signs that things are getting much better – at clubs such as West Ham and Arsenal in particular. But there are also gay people who are worried about what to do. The whole game needs to be much more open."

Positive developments include Arsenal's solid backing for the Gay Gooners supporters' initiative, while West Ham player Matt Jarvis recently became only the third footballer to feature on the cover of the gay magazine, Attitude, after David Beckham and Freddie Ljungberg. Jarvis said it was about time a gay footballer felt comfortable enough to come out, adding that doing so could even help an individual's playing performance, although he later revealed that following his appearance on the magazine his wife has been repeatedly asked about his sexuality.

Matthew Todd, the editor of Attitude, said footballers remained unusual in that most seemed afraid about being featured in a gay magazine.

• This article was amended on 8 May 2013. Originally, it had said that Robbie Rogers had left Leeds United by mutual consent after declaring he was gay. He actually came out as gay one month after leaving the club.