Armand Doorn, a man said to work for Ba's management team, says the Red Devils have joined the list of clubs weighing up a January approach for the Senegal international.
With it having come to light that Ba has a release clause included in his Newcastle contract, speculation regarding his future on Tyneside has been steadily mounting.
He only linked up with the Magpies last summer, following West Ham's relegation out of the Premier League, but it is being strongly suggested that he could be on the move again during the winter transfer window.
Doorn has fanned the flames by claiming that Manchester United have joined the chase, with the Red Devils having expressed an interest without making a formal approach.
Ba, though, claims to have no working relationship with the representative in question and has sought to bring an end to the incessant rumours.
"Really, I don't know how desperate this "armand doorn" can be to talk like he's my agent!!" Ba posted on his official Twitter account.
"He's nothing for me. Stop lying and show respect."
Ba's actual management team have also rubbished the comments made by the rogue agent, with a spokesman telling talkSPORT: "Armand Doorn is not Demba's agent. Alex Gontran is the only person who can speak on his behalf and Newcastle have not had an offer for him.
"Demba feels good at Newcastle. He has just started something there. There is a release clause in his contract but the figure will remain confidential.
"If a club wants to speak to Demba, then they must go to Newcastle first. We respect the process."