Jenson Button has revealed major doubts over Mercedes' return led to his move to McLaren in 2010.

The Briton had just completed one of Formula 1's biggest fairytale stories by becoming world champion with Brawn GP, a team that rose from the ashes of Honda after they pulled out at the end of 2008.

However, rather than be a part of the new Mercedes project, which was instead headed by Nico Rosberg and Michael Schumacher, Button opted to join Lewis Hamilton at McLaren.

"They 100 per cent wanted me to stay and I knew that Mercedes was buying the team," he told F1's Beyond the Grid podcast.

"I remember sitting in Dubai with Ross [Brawn] and Nick Fry and Richard my manager discussing it, they were like, 'Yep, they're going to buy the team but they're not going to fund the team through the year, the funding for the team and developments would all be through sponsors'.

"I was like, 'Hang on, really?' [And they were] like, 'We're going to get sponsors, they're going to pay for the development of the car through the year and Mercedes are going to own the team'.

"I was like, 'Well that doesn't sound very promising and a little bit worrying in a way'."

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Despite the success of Brawn GP, Button explained that the chances of the team fighting for the title again were slim due to the restraints of the previous year.

"I also knew that, through the 2009 season, we hadn't developed the car and I knew they hadn't really worked on the 2010 car, and Ross also said that," he continued.

"So for me, it was an uncomfortable position to be in after winning the championship, to be [potentially] racing for them in 2010 [in] a new project that I wasn't sure if it would have the right funding.

"Whereas you look at McLaren, a team that looked very strong at the end of 2009. I knew they would give me opportunities to win every year I raced with them, so it was a no-brainer really."

Button's scepticism would be justified initially as Mercedes did indeed struggle to keep up with McLaren, Red Bull and Ferrari, however, as we now know, those early years were essentially preparation for what came in 2014.

"Nobody could foresee what would happen with Mercedes five years down the road and I actually think the reason why Mercedes has become so big is because they had such a tough year in 2010," Button suggested.

"I think they were embarrassed as a manufacturer and thought, 'We can't have this' so they threw so much money at it and this is the monster we have now!"