US regulators have charged Credit Suisse First Boston (CSFB), Merrill Lynch and Citigroup with issuing fraudulent research as they unveiled an historic $1.4bn (€1.3bn) settlement over conflicts of interest on Wall Street.

Regulators, led by the US Securities and Exchange Commission (SEC) and Eliot Spitzer, New York State attorney general, presented the agreement on Monday after months of legal wrangling.