The US has published further guidance on its tax evasion law, reserving the strictest reporting requirements for private bankers, just days after it launched an offensive against HSBC India, demanding the firm hands over details of American clients suspected of hiding assets.

Under the Foreign Account Tax Compliance Act, the first stage of which comes into effect on January 1 2012, all foreign financial institutions with US clients will be obliged to disclose information on US taxpayers, with at least $50,000 of assets, to the Internal Revenue Service.