Expressing concerns over the fast-growing grey market in the financial sector, the Securities and Exchange Board of India (SEBI) Chief U K Sinha on Wednesday, called for a single watchdog to regulate all entities collecting public money under various illegal means.He also pointed that these deposit-taking firms were taking advantage of the loopholes in existing laws and the market regulator has raised the issue with the government. The comments come at a time when Sebi is fighting a long- drawn case against Sahara group, which has been asked by the Supreme Court to refund over Rs 24,000 crore raised from over three crore investors through issuance of certain bonds without Sebi's approval. Sebi has been to facilitate the refund after ascertaining the genuineness of investors. Without naming Sahara group, Sinha said today that a company recently claimed that it has refunded Rs 20,000 crore to the investors, of which 90 per cent in cash in the last 3-4 months period. Sinha further said that Sebi is worried over the rapid growth of the grey market in the financial sector and called for a single watchdog to regulate companies taking deposits from the public illegally.