John Amaechi described anti-gay sentiment in sporting institutions and on the pitch as a "massive problem" that was often ignored or "relegated".
He said: "I think people approach bigotry like there's a hierarchy. Homophobia has always been to the bottom of that ladder.
"In sport there are institutions that haven't changed in 100 years and need to."
Singling out the Football Association, he accused it of an abject failure to do enough to tackle the issue.
"If you compare their emphasis on racism to what they've done on homophobia it's an embarrassment," he said.
"There are people in the FA who aren't that pleased with the idea of women in the boardroom, never mind gay people."
And although he praised as "remarkable and very grown up" the response of the England and Wales Cricket Board to England wicketkeeper Steven Davies' decision to come out, he added that "there's still a lot of work to do".
Former England centre Amaechi spoke out after receiving his OBE from the Prince of Wales at a ceremony at Buckingham Palace.
He was honoured for services to sport and to the voluntary sector.