Button and rival Hamilton begin their sparring

Lewis Hamilton, left, and Jenson Button and compare pictures at the launch of the McLaren-Mercedes MP4-25 Formula One car at Newbury yesterday. The pair will go head-to-head for the same team this seaShow more

Jenson Button and Lewis Hamilton, the all-British line-up at McLaren-Mercedes, have pledged to fight fair in their battle to be crowned world champion at the end of the season. The McLaren duo took the wrapping off the team's 2010 car, the radical-looking MP4-25, in England yesterday, which will be driven for the first time in Valencia on Monday.

Team boss Martin Whitmarsh insisted Button, the world champion, would get equal billing with Hamilton, despite the fact the 2008 title winner is now in his fourth season at the team. And Button, who has joined the team from Brawn GP, described the challenge of fighting Hamilton for McLaren supremacy and the world title as the "ultimate challenge". "I'm excited, the most excited I've ever been going into a season," said the 30-year-old."It's a massive challenge to defend a world title and to beat a driver of Lewis' calibre but that's what I'm setting out to do. We'll both be going all out to win every race and be world champion but we'll do it fairly."

Hamilton dismissed suggestions that as McLaren's established driver he would get preferential treatment from the season-opening grand prix in Bahrain on March 14. "What you guys need to remember is that Jenson's the world champion," said the 24-year-old. "What he achieved last year was fantastic. To be on the same team as him and with us both having been world champions it's the perfect partnership."

Hamilton insisted he had no desire for a repeat of the fractious relationship he endured with former teammate Fernando Alonso during his rookie year in 2007 and said he would take a different approach alongside Button. Hamilton said: "We need to work together as a team. In 2007, we [he and Alonso] didn't work together well enough in some cases. You need to understand the need to work together to push the team forward. We want to beat each other fairly and squarely; we want to win the constructors' and one of us to win the drivers' championship."

McLaren suffered one of their worst starts to a season in the team's history as they scored only 14 points in the first nine races of last season. In the end, the team turned the MP4-24 from a woefully uncompetitive car to become a race winner in Hungary and Singapore for Hamilton. After seeing this year's car for the first time, which features a new high shark-fin engine cover, Hamilton said he was confident it would be much improved on 2009. "The car looks completely different to last year's car," he said. "I can't wait to get on the track with it and I'm sure it's going to handle completely differently to last year's car."

McLaren are among the favourites to win both the constructors' and drivers' crown but look likely to face opposition from Red Bull, Ferrari and a Brawn team rebranded as Mercedes and with Michael Schumacher at the wheel. Hamilton admitted he was relishing the opportunity to take on the seven-time world champion. "I was lucky enough to be on track with him a couple of times in tests and it was great to see the Schumacher Ferrari then," he said. "I'm looking forward to either seeing him in my wing mirrors or in front of me on the road."