The future of Jaguar and Land Rover seemed to be in the balance last night after owner Ford slumped to its worst quarterly loss for 14 years.

Newly-installed group chief executive Alan Mulally refused to commit to retaining the two West Midland brands in wake of a massive deterioration in the group's finances.

In fact, Ford revealed that it had wiped £851 million from the book value of the two operations to reflect their declining importance to the world's third-largest carmaker.

On top of that, it said the warranty cost of rectifying faults in Jaguars and Land Rovers had contributed to a big increase in losses at Premier Automotive Group (PAG), the stable of European luxury brands that also includes Volvo and Aston Martin, which is already up for sale.

PAG showed a loss of £315 million in the third quarter of this year compared with a deficit of £57 million in the same three months in 2005.

Automotive industry commentators believe Jaguar, a persistent loss maker which became part of Ford in 1989, has been a disposal candidate since Wall Street troubleshooter Kenneth Leet was recruited by group chairman Bill Ford to review all of Ford's operations.

Aston Martin was put on the auctioneer's block in September but Mr Ford said at the time that he had no plans to ditch Jaguar.

The theory is though that Mr Leet could recommend not just selling the company, which makes three of its four models at Castle Bromwich after abandoning its historic Browns Lane site in Coventry, but also throwing in Land Rover as bait for potential buyers.

Mr Mulally last night said Ford had invested heavily in new models and in improving quality and productivity.

But when he was asked whether he felt he could commit himself to keeping the PAG brands he said: "No, I don't."

He went on: "I really think it's going to hinge on how the businesses are doing and whether we can make profitable growth businesses out of them with the actions we have taken and the additional actions that might be required."

Group losses at Ford soared to £3.085 billion between July and September, the biggest quarterly deficit since the first three months of 1992 and 20 times worse than in the same period last year.

Losses for the year so far now total £3.9 billion and there is a fear that the deficit for the full 12 months could approach, or even exceed, the £5.6 million stacked up by General Motors in 2005.

Ford has now been in the red for eight of the last nine quarters and the latest tidal wave of red ink means this is now a "critical time" for the group, according to Mr Mulally, a recent recruit from Boeing.

"These business results are clearly unacceptable," he said.

Like its big Detroit rival GM, Ford has been battered by the storm whipped up by some major changes in its key North American market.

The cost of the generous pension and healthcare deals with its workforce has become unsupportable at a time when sales are ebbing away in the teeth of intense competition from Asian rivals such as Toyota, whose US sales recently overtook those of Ford.

At the same time its customers are turning their backs on gas-guzzling trucks and SUVs, its most profitable products.

Third quarter sales at Ford fell by £2.2 billion to £20 billion as consumers shunned its vehicles in favour of more fuel-efficient offerings from overseas manufacturers.