Investors in South Korean companies have complained about a ?draconian? requirement to disclose the identities of their chief backers to the country's Financial Supervisory Service by the end of this week.

The sudden move applies to the shareholders or sources of capital of any company or fund owning more than 5 per cent of a South Korean business. It tightens controls on foreign investors, who had been told to declare by Tuesday night whether they planned to ?influence? the managers of South Korean companies.