Button is at the centre of a high-profile tug-of-war

A BAR statement on Tuesday said Formula One's Contract Recognition Board had backed their claim on the driver.

But Williams insisted the CRB had "not endorsed the validity" of BAR's claim, merely confirmed receipt of their documents.

Button has told BAR he is committed to his decision to sign for Williams.

A statement by Williams insisted that "does not mean [BAR's] contract is valid, or holds precedence over other contracts with Jenson Button".

Williams added: "It is Jenson's intention to drive for the team in 2005 and that his contractual position allows for this."

Williams reiterated that they lodged a contract with Button with the CRB in October 2002.

The team also repeated their belief that BAR "have failed to correctly exercise certain options in their contract with Jenson Button and, as such, their contract has expired, and Williams' contract is valid".

BAR dig in over Button

Button and his advisers also insisted last week that they have a contractual right to leave BAR and switch teams.

The CRB was established in 1992 to resolve disputes two rival teams claim to have valid contracts with a driver.

The BAR statement said: "A driver's super licence, his right to drive in Formula One, is only valid if his contract has been lodged with and registered by the CRB.

"Any new driver contract (must be) registered 'forthwith', in other words immediately, and without delay, in order to establish its validity.

"BAR has willingly submitted itself to this process, which is final and binding on all parties."

Williams disagrees with that assessment, insisting that "the CRB does not, in all cases, make final adjudication on contractual disputes, and may refer cases to the appropriate legal authorities".

Williams added that it "has a commitment to correctly represent the outcome of this process to the media as and when a conclusion is reached".