London Premier League club Tottenham Hotspur proposes to remove the track if its bid to move into the east London venue succeeds ahead of West Ham United. The two clubs will make their final submissions to the Olympic Park Legacy Company (OPLC) on Friday.
International Association of Athletics Federations (IAAF) president Diack said in a statement the promise of an athletics legacy had been a key part of the London bid team's successful submission to the International Olympic Committee in 2005.
"This promise was not a footnote of London's bid: it was a core policy of their presentation to convince the Olympic family of their exciting, viable legacy plans," Diack said.
"There is no doubt that this commitment played its part in the UK winning the right to host the 2012 Games.
"While concerns have been raised about sightlines for football we should recall that football has often shared with other sports and not just outside the UK.
"Five out of the last six Champions League finals have been held in stadiums with tracks.
"To now demolish the Olympic stadium, throwing away the original 500 million pounds investment of public money, seems to me an outrageous proposition, especially in the present world economic climate.
"Instead, let us keep London's promise alive and leave an athletics legacy at the venue with a top football club as a valued partner."
"BIG LIE"
Earlier Diack, who is a member of the International Olympic Committee, told the BBC that London's 2005 submission would have been a "big lie" if the track were removed.
"They will have made a big lie during their presentation," he said. "There will be no credibility... of a great country like Britain. You can consider you are dead. You are finished.
On Wednesday, British Olympic Association chief executive Andy Hunt told Reuters the track should be retained in the Olympic Park.
"Our position is that we want the bid commitment to be met and that was for a track to be retained within the Olympic Park," Hunt said.
"The OPLC should make the decision but we are clear, we backed the bid commitment and the decision should be in line with that. I'm sure the right decision will be made by those responsible for making it.
"Our commitment is that we always wanted a track in this country that can allow us to bid to host a world athletics championships and other big events."
