Arturo Vidal is to launch legal action against German publication Sport Bild over claims he drank alcohol during the training camp in Qatar.
The report said that Vidal arrived for a handful of training sessions during Bayern's mid-season trip to Doha after drinking.
The claims follow previous reports that Vidal is at the centre of dressing-room unrest within Pep Guardiola's squad, with the head coach allegedly unimpressed with the Chile international's fitness levels.
But Vidal has hit back angrily at the allegations and insists he is fully committed to the club.
"I would like to say that the 'news' published today in a German newspaper are [sic] absolutely false," he wrote in a statement released via Twitter.
"My lawyers have been already instructed to initiate a legal claim against the newspaper, which will be responsible of [sic] their lies.
"I'm 100 per cent committed to my team and preparing the rest of the season that will be very important for all of us.
"Thanks to my club for their support and also thanks to all my fans that show me all their love as always."
Sporting director Matthias Sammer later accused the media of attempting to "degrade" Bayern through false allegations and said the relationship between player and club remained strong.
"It is not the truth," he said, speaking at a media conference on Wednesday. "Our relationship with Arturo is very good and he told us that all the rumours are fake.
"The media tries to build a situation that degrades us in the Bundesliga. But the entire disturbance will make us stronger as a team."