Bernard Madoff left behind a trail of “falsified” and “unreliable” records, hampering efforts by investigators to unravel the mystery of the $50bn “Ponzi” scheme allegedly perpetrated by the New York broker, officials said on Tuesday.

Stephen Harbeck, president of the Securities Investor Protection Corporation, an industry-funded body set up by Congress to help investors in failed brokerages, said it could take at least six months to “get a handle” on the situation.