Toyota, the world's biggest carmaker and a symbol of Japanese industrial power, has been stripped of its AAA credit rating for the first time in a decade under the darkening global economic storm.

The downgrade, analysts for Fitch Ratings said, effectively passed a verdict on the entire worldwide motor industry, showing that the business of building cars can no longer produce a single player with the sort of cast-iron corporate resilience of ExxonMobil or Johnson & Johnson.

“This crisis is demonstrating that the auto industry cannot support a triple-A rating,” said Frederic Gits, a Tokyo-based credit analyst for Fitch, which issued the downgrade yesterday and declared the car industry's problems “substantial and fundamental”.

Fitch's downgrade of Toyota's unsecured debt to AA is not only a blow to Japanese corporate pride, but also reflects “severe” turmoil across world car markets and the carmaker's own spectacular profit warning this month.

Two weeks ago and citing a dramatic collapse in US and European sales, Toyota cut a trillion yen (£6.8 billion) from its full-year earnings estimates. If the company hits its new estimate of ¥600 billion for the year to March 31, it could even lose its crown as Japan's biggest profit-generator. The fall of 63 per cent in Toyota's own profit forecasts comes as production is being slowed in various places throughout its empire, and the company has been forced to introduce no-interest loans as enticements in the US and Europe.

Mr Gits said: “A triple-A rating should mean that the company can withstand any shock.

“Although the auto industry is not one that you would think of typically as supporting a triple-A rating, because of its inherent cyclicality, we thought that Toyota's strong market positions, cashflow strength and very substantial financial flexibility were sufficient to deserve the highest rating. However, we are seeing that even the strongest player can suffer when you have such a deep economic shock as we are now experiencing.”

Toyota, in common with other Japanese exporters, has also seen margins annihilated by the rapid rise in the yen against the dollar and the euro — a side-effect of the collapse of global stock markets and the mass unwinding of the yen-denominated “carry trades” that financed so many speculative bubbles. The yen's gains in the past two months have carved a ¥690 billion hole in Toyota's profits, and caused proportionally similar pain to Sony, Canon and Honda.

However, Fitch's downgrade chiefly highlights the harm done to car sales everywhere by the financial crisis. Even after the downgrade, Toyota is by far the highest-rated carmaker. The next strongest global player is Honda, whose debt rating is a full two notches below that of Toyota. America's carmakers are many levels below that, and even the strongest German players, Daimler and Volkswagen, do not rival Toyota in ratings strength.

Behind Fitch's downgrade is a fear of capitulation by consumers in Asia. High hopes for the sales prospects of Japanese and European carmakers were formed amid optimism over Asian growth and expectation that millions of Chinese and Indians would soon switch from scooters to cars. That process has slowed substantially and may be due for a much nastier spasm than the market has realised until now.

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