A row has been brewing this week over a virtually all-white set of Oscar nominees. It has prompted directors Spike Lee and Michael Moore, and actor Will Smith, among others, to boycott next month's awards ceremony in Los Angeles.It has also led to the academy's board of governors issuing a hasty pledge to double the number of female and minority members in its ranks by 2020.None of this came out of the blue. A year ago there was an almost identical flash point when all 20 of the performers nominated were white.For his role as Martin Luther King in Selma - a great, bruising film and one of last year's best picture contenders - British actor David Oyelowo received universal acclaim and a Golden Globe nod, but no Oscar nomination.Selma's director, Ava DuVernay, who deserved to become the first black woman to make the best director shortlist, was snubbed.At last year's ceremony there was a moderate outcry, plenty of pointed jokes, and a general feeling that Oscar voters needed to wake up to the future.It wasn't at all okay to point to the three awards they had bestowed the year before on 12 Years a Slave - for best picture, its black screenwriter, John Ridley, and supporting actress Lupita Nyong'o.No one could seriously argue that those prizes gave academy voters carte blanche, as it were, to ignore black themes, and artists, the following year. Not least because repetition has never been a problem for Oscar voters - the one non-white director to make the shortlist this year, for The Revenant, is last year's winner, Birdman's Mexican virtuoso Alejándro G Iarritu.This year, the academy's voters barely had to look beyond their noses to see exceptionally deserving black nominees.Idris Elba is up for a Golden Globe and a Bafta for his career-topping work as an African warlord in the child-soldier drama Beasts of No Nation. You don't even have to like Elba - I'm far from his biggest fan, as it happens - to recognise how special his performance is and what a terrific fit it represents between actor and role.It's the kind of part that tends to help a very popular and respected star to join the ranks of the Oscar-anointed. Somehow, though, the Londoner lost out. He wasn't pipped to it by the Puerto Rican Benicio del Toro in Sicario, whois another Bafta nominee missing from the best supporting actor category - but by five white stars.One of these is Sylvester Stallone, who absolutely merits praise for his seventh performance as Rocky Balboa in the sequel-cum-reboot Creed.However, in a horribly unfortunate turn of events, Stallone's nomination only adds to the cringeworthy situation: it's the sole recognition voters have given to a film made by an extraordinarily talented black writer and director, Ryan Coogler, and starring an equally outstanding black lead actor, Michael B Jordan.Rocky won best picture back in 1977 and was nominated for 10 awards in total, including four for acting. Reviewers have lined up to call Creed the best film in the series since then and it's been a commercial hit beyond Warner Brothers' wildest hopes.Yet all it gets from the academy is a single, white, nomination. Did Warners campaign ardently enough for Coogler and Jordan to be cited? Perhaps not. But this only underlines the wider struggle that black artists still face to be recognised within the industry.Responses to this escalating controversy, such as best actress nominee Charlotte Rampling daftly declaring it "racist to white people", have stoked the flames still higher.A 2014 study found that academy members were 94% Caucasian, 77% male and had an average age of 63. The commitment the academy's black president, Cheryl Boone Isaacs, made this week, to "changing our membership composition", is long overdue.But it's not just in the area of race that the academy needs to step up its fight for relevance: to date only four women have been nominated as best director, with Kathryn Bigelow the sole winner.This myopic outlook has created an ever-widening gulf between the films that audiences enjoy and those that voters will even consider for awards, a gulf that increasingly threatens the academy's credibility.Oscar voters need to open their eyes, fast. They might well begin that process by asking themselves, hand on heart, if the best 40 performances in cinema over the past two years really were all given by white people...