West Ham are taking legal action against Tottenham and The Sunday Times over allegations surrounding the validity of the Olympic Stadium bidding process.
The club said they were treating claims made by the newspaper "with the utmost seriousness" and insisted they were "certain of the robustness" of their successful bid to take over the east London stadium following the 2012 games.
It comes days after the Olympic Park Legacy Company (OPLC) confirmed an employee had been suspended after it was discovered she was working as a consultant for West Ham during the bidding process.
The woman has been suspended with immediate effect while the potential clash of interests is investigated.
A West Ham spokesman said: "West Ham United can confirm the club are taking legal action in relation to allegations made in today's Sunday Times.
"We are certain of the robustness of our successful bid for the Olympic Stadium.
"The OPLC board, in charge of securing the future of the Olympic Park site, voted 14-0 in February to make the Hammers the first choice to move into the £486 million stadium. They were in a head-to-head contest with Tottenham."