Allen Stanford was 'US government informer'

A former law enforcement official said in February that the FBI and other agencies started looking into Sir Allen's possible involvement in money-laundering in the 1990s but could not find sufficient evidence to charge him.

Panorama claimed some US officials were aware of Sir Allen's cartel links as long ago as 1990. It reported that Sir Allen, paid a $3.1 million (£2.05 million) cheque to the DEA in 1999 after that sum was invested in his bank by another Mexican drug gang, the Juarez cartel of Amada Carillo Fuentes.

According to Panorama, whose investigation will air on Monday, Sir Allen was initially investigated by the SEC over suspicions he was running a Ponzi scheme in the summer of 2006, but the inquiry was over by the winter of that year.

The BBC claims the decision to close the investigation followed a request by another government agency.