A set of studies into the attitude of football fans towards gay people has revealed dramatic changes in the last 25 years, with many saying the sex lives of professional players are “entirely up to them”.

Dr Jamie Cleland, a lecturer in criminology at Loughborough University, said his research showed 93% of fans believed a player’s on-field performance, not his sexuality, was the most important thing to them.

“People said that when they took their car to the garage they didn’t ask about the sexuality of the mechanic. They said what Rooney and Ronaldo get up to in their spare time is entirely up to them,” he revealed.

Dr Cleland conducted studies analysing the views of 3,500 football fans towards gay players, as well as looking at discussions of homosexuality on online football message boards and the media’s reaction to Swedish footballer Anton Hysen coming out in March 2011.

He said the environment in football had “changed dramatically since the 1980s and 1990s”, but added “there is always a vocal [anti-gay] minority – and they are very vocal.”

The study was prompted initially by the Football Association’s decision to drop an anti-homophobia campaign in 2010 because football was “not ready”, and by PR guru Max Clifford’s claim he had advised two Premier League players from coming out as “football remained in the dark ages, steeped in homophobia.”

Dr Cleland said this stigmatised fans unfairly, and added he had found that members of online football message board would often criticise homophobic posts.

He said: “When I analysed these online fan sites, someone would make a homophobic post and very quickly fans would jump on it. And they wouldn’t let it go.

“What struck me, looking across nearly fifty fan sites, is that fans are willing to self-police and challenge homophobic posts.”

Despite changes in attitudes, there is currently only one gay professional footballer, Anton Hysen, who plays for Swedish third division side Utsiktens BK.

Dr Cleland said 84% of fans blame clubs and agents for pressuring gay players not to come out, adding “clubs are very protective of their brand”.

However, he said the representation of “metrosexual” players like David Beckham in the media have helped changed attitudes over recent decades.

“A lot of men now admire players like Beckham and Ronaldo who, to coin a media term, are metrosexual men. They are not afraid to be associated with some form of femininity,” he said.

Dr Cleland believes football would benefit if a high profile Premier League player came out, saying: “Football needs to move with the times.

“We have an openly gay cricketer, Steven Davies, and a gay ex-rugby union/league player, Gareth Thomas, who was hugely respected. At some point we will see a gay footballer playing in the Premier League. And the sooner it happens the better.”

Dr Cleland’s research has been released the same week as Minister for Sport Hugh Robertson backed calls for professional clubs to do more to combat homophobia.

Earlier this week Sussex Police has promised to trace several Crystal Palace fans following a spate of homophobic incidents during Sunday’s match against Brighton and Hove Albion.