BBC radio DJ Nihal has criticised diversity at Radio 1, claiming "nothing has changed" at the corporation since former director general Greg Dyke called it "hideously white" in 2001.
He welcomed news that DJ Clara Amfo is joining Radio 1's daytime line-up.
But he said there is "a problem on the eighth floor" of the BBC's Broadcasting House where Radio 1, its sister station 1Xtra and the Asian Network are based.
The Radio 1 office, he said, is "all white" while 1Xtra's is "all black".
The former Radio 1 DJ, who now broadcasts on Asian Network and 5 Live, was taking part in a panel on diversity at the Oxford Media Convention when he made his comments.
"All the Asians are sitting in one corner, all the white people are on Radio 1 and all the black people are on 1Xtra," he said.
"That is not diversity, that is silos."
In a statement, the BBC responded: "Radio 1 and 1Xtra are committed to reflecting the diversity of their young audiences and these sweeping generalisations are untrue.
"Both stations have exceeded the BBC's diversity targets and we will continue to work hard to build on this progress."
Nihal - full name Nihal Arthanayake - is currently part of BBC director general Tony Hall's working group to improve diversity at the corporation.
He praised the way Lord Hall is tackling the issue and expressed gratitude for the opportunities that have come his way.
"I was a Radio 1 DJ for 12 years, one of the most amazing experiences of my life," he told BBC News after his Oxford appearance on Wednesday. "Only the BBC would have given me the opportunities I've been given.
"But that's not to say I can't criticise the BBC, as others do, for where it can be better. We need to work harder.
"It's 14 years since Greg Dyke made his 'hideously white' comments. In 14 years my seven-year-old son will have left university, he'll be 21.
"I don't want to be having the same conversation then."
Last week Radio 1 announced that Clara Amfo, who recently took over presenting the station's Official Chart show, will replace Fearne Cotton when she steps down as the host of weekday mornings.
"I think it's amazing that Clara Amfo is going to be in charge of the Live Lounge," Nihal told the BBC.
"She is a fantastic broadcaster who is there purely because of that. It's such an important thing that has happened, and it's happened because of merit."
By introducing the first black woman to its daytime schedule, he said, Radio 1 and Amfo would "give lots of women of colour the sense that they can do this, that Radio 1 is not a place that's not for them."
'Need for sanctions'
However, Nihal - whose fellow panellists at the one-day media festival included politician Oona King - pointed out that "two thirds of the room left to go to another panel when it was announced that we were going to talk about diversity.
"There were no ethnic minorities in the audience at all. The only ethnic minority people that were in the room were on the stage."
During the discussion, he also suggested the issue of diversity was about class and not just about colour.
"Class is at least as big a problem," he told the audience. "If you just put Oxbridge brown people in positions, then what's the point? They come from exactly the same mindset. That's not diversity, it's a fig leaf."
However, he said the diversity working group at the BBC - which also includes broadcaster Floella Benjamin and comedian Lenny Henry - felt a lack of sanctions was a problem.
"If you don't achieve these targets, nothing happens… and they try again in five years when it becomes politically expedient again.
"That's the reason people are scared of quotas, because it forces them to do something."
"I'm a born optimist and things will get better, they're already getting better," Nihal told the BBC.
"But in five years time the BBC should be fully representative of the audience it serves."