West Ham's hopes of moving to the Olympic Stadium could be affected by lowly Leyton Orient.
Last week the Hammers were given a major boost when they were named as 'preferred bidders' for the Olympic Stadium.
It meant they were almost certain to move there after the London Games in 2012 having beaten off the rival claims of Tottenham Hotspur.
But now Leyton Orient - who play in League One, two divisions below West Ham - are challenging the decision.
Orient chairman Barry Hearn believes that if West Ham do move from Upton Park, they could attract supporters of his club, whose Brisbane Road ground is close to the Olympic Stadium.
Hearn has written to British prime minister David Cameron, London Mayor Boris Johnson and Olympics Minister Hugh Robertson in a bid to reverse the ruling.
One of his options is to launch a judicial review challenge at the High Court.
"It's a question of due process and whether the Olympic Park Legacy Committee, the Department for Culture, Media and Sport and even the Prime Minister have given consideration to Leyton Orient in these discussions," said Hearn.
"The government has a responsibility to take into account all the effects of any ruling they take."
"We are awaiting what I assume is a rubber-stamp decision from Boris Johnson and the DCMS to award West Ham the stadium."
"But I find it incredible they would even consider making the decision before undergoing due process in regard to the effect on the incumbent football club."
Among Hearn's concerns are West Ham's indication that they would give free or heavily discounted tickets to local residents in a bid to fill the 60,000-capacity stadium.
He believes that would badly impact on attendances at Brisbane Road, where the average gate is around 4,000.