Three-time world champion Niki Lauda believes there is not "one single grain of truth" in reports linking Michael Schumacher with a move to Mercedes GP.

Mercedes are yet to confirm Nico Rosberg's partner for next season and seven-time champ Schumacher has been strongly tipped to come out of retirement to form an all-German line-up.

Although team boss Ross Brawn denied the rumours by claiming it is nothing more than a "dream", Mercedes motorsport boss Norbert Haug remained coy when he was asked about the possibility of Schumacher joining the team.

Lauda, though, believes the rumours are pure hogwash as it is unlikely that Schumacher "would be up for a full season" of F1 racing.

"I don't believe that there is one single grain of truth in them, at least from all the signals that I get," he told the official Formula One website.

"There was a window of opportunity after Felipe's (Massa's) accident and had Michael been fit he would have taken up that chance to race for three or four races - to prove himself, get the adrenaline rush, and see where he stood in the pecking order.

"But I cannot believe that he would be up for a full season. Why then he did stop racing in the first place? But that is my personal opinion."

World Champion Jenson Button's decision to swap Brawn for McLaren has raised a few eyebrows, but Lauda says it's "not really" a surprise.

"That was a true 'Ron Dennis' move - to run a team with two British world champions," he said. "On the other hand, I am sure that Ross (Brawn) was not completely satisfied with Jenson's performance in the second half of the season.

"But if Mercedes ends up with someone not as good as Jenson, then they've drawn the short straw. I would not have an idea who they should take."