Standard & Poor's, the international rating agency, is threatening to downgrade Sony Corporation, the Japanese electronics giant, following its $5bn (€4.1bn) acquisition of Metro-Goldwyn-Mayer, the loss-making US movie studio.

The rating agency said: "Although details about the deal are unclear at this point, the acquisition may raise Sony's funding requirements by a larger amount than was originally expected under the company's medium-term business plan. This could cause deterioration in Sony's balance sheet and hamper structural reform."