LONDON, Oct 10 (Reuters) - Prodrive have ruled out using identical cars to McLaren in next year's Formula One
championship, with their planned entry as the 12th team looking increasingly uncertain.

"We cannot do the plan that we had with McLaren now," team boss David Richards told Reuters on Wednesday.

"There will not be a full-blooded equal car arrangement from day one, it cannot be," he added, while refusing to rule out the possibility of running a 'hybrid' version or alternative chassis.

Prodrive had agreed a deal with McLaren to use the same cars as the Mercedes-powered team next year but the plan has been thrown off track following a challenge by Williams.

The governing International Automobile Federation's international court of appeal is due to rule on the legality of
Prodrive's entry after a hearing in London on Oct. 24.

However there is the risk of further legal action in the civil courts beyond that, with former champions Williams
fighting what they see as a battle for survival as an independent constructor.

The Formula One rules are due to be changed next year to allow for so-called 'customer cars', which are illegal at
present, but the existing teams have yet to sign a new commercial 'Concorde' agreement for the sport.

Entries for the 2009 championship have also yet to be agreed by the FIA.

Williams say teams that do not make and design their own cars should not be allowed to score championship points or benefit from television revenues earmarked for constructors.

COMMERCIAL THREAT

"The Concorde Agreement is an agreement in law, it covers commercial matters which the FIA have been told by the European Commission that they are not supposed to be involved with," Williams co-owner Patrick Head said last weekend.

"They have been told they must not interfere in commercial matters.

"Obviously if a team comes into Formula One without any investment in the staffing and equipment that we've built up over the last 25 years and gains access to a (customer) car...then its a serious commercial threat to us."

Prodrive said in a statement that while they remained confident "that the short term issue of eligibility to race in
2008 will be resolved in our favour, it still leaves the question of longer term stability unanswered.

"It is Prodrive's opinion that the financial viability of a new team will not be possible until agreement is reached on a
revised Concorde Agreement."

Prodrive said they could not hire staff or take on major financial obligations while such issues remained unresolved.

"Prodrive remain committed to participating in Formula One," Richards said.

"We are hopeful that the current dispute over our eligibility to race will be clarified at the hearing later this month and that a Concorde Agreement between the FIA, FOM and all 12 teams can be established in the near future.

"In the meantime, we will consider all our alternative options for next season."