The reigning World Champion confirmed that he had departed Brawn despite the team offering him more money than he will be paid to partner Hamilton.
In an interview with the BBC, Button also revealed that he has yet to speak to Hamilton since making the transfer, and he spent Wednesday at Brawn’s Brackley base making his farewells to the team with which he spent seven years.
“It was 100 per cent my choice. I thought the challenge of going up against Lewis in his environment would be exciting,” he told Radio 5 live. “I’m earning less than I would have at Brawn, so it’s not for money – everyone involved knows that’s the case.
“I feel like I needed a new challenge. I’ll be earning less than I did at Brawn, so it’s not about the money. It’s because I wanted something new.”
“I know I’ll have to work hard to achieve what I want in 2010.”
Button admits his decision, which means the Woking-based company now have the last two world champions in an all-British star line-up, did not come easily.
“I was excited but there was a lot to think about because I’d been with Brawn for seven years,” he added.
“On the emotional side there was definitely a lot to think about but I thought the challenge of going up against Lewis in his environment would be very tough but very exciting.
“I know the environment in both areas and I know what I want to do and I want new challenges.”
Button also paid tribute to Brawn – “I couldn’t have done it without him” – but accepted things will change from now on after he said goodbye to the Brawn mechanics.
“It’s going to be a different relationship because I am not within the team any more, we’re not fighting for a world championship together,” Button added.
“We’ve achieved that goal so I am going to be a rival. We’ll still have a good relationship, we’ve been through a lot together.”