MERRILL Lynch, the world's largest stockbroker, yesterday sought to play down newspaper reports that it was the latest of a growing number of major financial firms to suffer "accounting irregularities". An internal investigation by the firm into its trading derivatives arm is chasing up unreconciled transactions - not any "black hole". City watchdog, the Securities and Futures Authority, confirmed yesterday that there was no formal probe into Merrill's affairs, contrary to a report in the Guardian newspaper.