Ratings agency Fitch has downgraded Toyota one notch to A, with a stable outlook, citing "the prolonged inherent structural weakness that leaves it vulnerable to FX (foreign exchange) volatility".

"Fitch estimates that Japan accounts for about 40% of Toyota's global production, and Toyota exports around 50% of its Japanese production which is higher compared with its Japanese competitors. As a result, the company is the most exposed among the big three Japanese automakers to FX movements and its profitability improvement was slowest among its Japanese competitors."

Toyota said recently it would no longer export its Camry model to North America, relying solely on US production, but a spokesman refused to be drawn on whether the move was related to exchange rate concerns.