Leyton Orient chiefs have started a legal fight to have the decision to allow West Ham to move into the Olympic Stadium struck out, owner Barry Hearn has said.
The League One football club, which wants a ground-share at the £429 million venue, has asked for permission for a judicial review of the bid process.
He said: "The rules of the bidding process created by the London Legacy Development Corporation (LLDC) we do not believe provided for teaming, which is for all parties to share the stadium.
"It is our legal opinion that this is a fundamental flaw of the bidding process.
"We have gone to the High Court to have the decision struck out."
The LLDC board, which is tasked with sorting out the stadium's future, named West Ham as the number one choice to move Olympic Stadium in December.
A LLDC spokesman said: "We have been notified that Leyton Orient have made the decision to issue proceedings for judicial review.
"Whilst this is disappointing, we believe that our processes have been robust, fair and transparent and that the challenge is misconceived."