West Ham say an independent review of the decision to make them the preferred bidder for the Olympic Stadium has found no evidence of wrongdoing.
The Hammers launched the inquiry after it emerged Olympic Park Legacy Company employee Dionne Knight had worked for the club during the bidding process.
A West Ham statement claimed the findings "completely exonerate" them.
But the OPLC is still holding its own investigation, which could put West Ham's stadium plans in jeopardy.
In February the Hammers were chosen to move into the ground, beating off competition from Tottenham, who want a judicial review of the decision.
On 1 July Knight was suspended by the OPLC after admitting she had worked as a paid consultant for the Upton Park outfit.
Reports claimed the payments were secret but West Ham insisted her work was "transparent".
"[The inquiry] concluded firmly that Ms Knight's work had in no way affected the integrity of the joint West Ham United-London Borough of Newham bid which was approved by the Olympic Park Legacy Company," the West Ham statement continued.
"The findings - which completely exonerate the club over the matter and showed it acted lawfully at all times - came after the consideration of all relevant correspondence and documentation, along with statements from all relevant officials.
"The report found no confidential information was passed by the OPLC to West Ham United through Ms Knight. Similarly, it found that no person at the club has at any point considered themselves to have an improper source of information or influence within the OPLC."
West Ham added that they would launch legal action against the Sunday Times and Tottenham.
The statement concluded: "West Ham remain in contact with police with regard to the serious matter of a private investigator acting unlawfully, reportedly under instruction by Tottenham Hotspur."