Amir Khan has accused an unidentified man of "interfering" with officials and the judges' scorecards during his defeat by Lamont Peterson.
Khan made the claims through Twitter by posting a number of images from last month's fight in Washington.
The Bolton fighter said the pictures highlighted his concerns about the appearance of a man at ringside.
Khan, 25, claimed the man talked to WBA supervisor Michael Welsh and interfered with the judges' scorecards.
His appeal against the controversial points decision to hometown fighter Peterson, which cost him his WBA and IBF light-welterweight titles, will be held later this month.
However, the IBF told BBC Sport that "with regards to the IBF master scorecard we can assure that it has not been tampered with", while the WBA is yet to respond.
Among a string of tweets, Khan alleges that the unidentified man started to "interfere" with Welsh in round six and continued to do so until the end of the fight.
He also claims that the man talked to Welsh and handled the scorecards, which were handed to Welsh at the end of each round, and that Welsh admitted after the fight that his scorecards did not match the others.
Last month Khan had told of his unhappiness with the performance of referee Joe Cooper - who deducted Khan two points for pushing - and alleged scorecard irregularities.
Khan's trainer Freddie Roach told BBC Sport he believes his charge "got screwed".
Roach said he wanted to see Cooper suspended from officiating future world title fights and that "the fight should 100% be looked into".
"I have no knowledge of any wrong-doing but it was unusual how long it took [for the scorecards to be tallied]," said Roach, Khan's trainer since 2008.
"Wrong-doing in boxing is always hard to prove but we got screwed in that fight. I hope something is done about it.
"I'd like to see the DC Boxing and Wrestling Commission look into the fight and I think the WBA and IBF - the sanctioning bodies - should be involved also.
Asked if his suspicions were aroused on the night, Roach said: "It goes through your mind [that there may be wrongdoing]. I mean, how hard can it be to add 12 rounds of boxing up?
"And Amir had two points deducted for pushing - the first time I've ever seen that."
Khan's business manager Asif Vali said they had written to the boxing authorities about the unidentified man.
"We don't know who the official is," he said. "We've asked the question, we've written to Washington DC and we're still waiting for their response, and we've written to the IBF and they've still not responded.
"If the answers are legitimate, fine, we'll accept them. If they're not legitimate, then we hope the rematch takes place, and if the rematch takes place, all this can be squashed."
