US regulators suspected Stanford in 1997

American regulators had concluded in 1997 that Allen Stanford, the sports-mad financier who bankrolled English cricket, was probably a fraudster, but they didn't charge him for 12 more years because it was too complicated a case.

Their inaction meant that a $250m fraud spiralled into a Ponzi scheme worth $8bn (£5.2bn), second in size only to Bernard Madoff's, and that Mr Stanford, pictured, remained free to enjoy the lifestyle of an international playboy.

Mr Stanford's financial empire was hidden largely offshore in Antigua, where he received a knighthood from the government for his services to the economy and to cricket. He was finally arrested last year and is awaiting trial in his native Texas, having denied fraud.

Details of the repeated regulatory failures were revealed last night in a damning internal report by the Securities and Exchange Commission (SEC), the US investment industry watchdog.

An inspection team from the SEC first investigated Stanford Financial Group just two years after it began selling certificates of deposit which promised suspiciously high returns for investors. Inspectors vainly urged enforcement action be taken after investigations in 1997, 1998, 2002 and 2004. It was only after Madoff stunned the investment world by confessing his crimes at the end of 2008 that the SEC went after Mr Stanford.

His arrest last February left thousands of investors uncertain how much of their money they would get back and caused embarrassment for the England and Wales Cricket Board, which had agreed a $100m deal with him to fund Twenty20 cricket.