Button in F1 storm as he goes back to Williams

Motor racing chief David Richards today threatened to challenge Jenson Button's shock defection from BAR to Williams.

Button announced he was returning to Williams in 2005 on a two-year deal despite having a contract with BAR.

He was able to get out of that agreement due to a clause which invalidates BAR's hold on him should they risk losing their works Honda engine supply.

BAR boss Richards described the clause as a "technicality" and, with Honda renewing their supply deal two weeks ago, he feels he has been taken for a ride. He said today: "About 36 hours ago we had a letter suggesting the option (on Button) wasn't viable based upon Honda's commitment to us. This is ridiculous and we will challenge it."

Richards has been unable to speak to Button since discovering his star driver's intention as the 24-year-old Englishman is on a break.

He added: "I have numerous emails from Jenson's management suggesting that it's a formality he will stay with the team. I am dumbfounded. I have 400 people who work their socks off night and day and then the guy who gets all the credit and drinks the champagne turns round and ditches them."

Williams technical director Sam Michael said: "Several days ago we were informed by Jenson's legal team that the BAR option had not been taken up and he was available. Our opinion supports Jenson's management, so as far as we are concerned the contract is valid."

Button will team up with Australian driver Mark Webber at Williams next season.