Fresh questions about the ECB's judgement over entering into a business partnership with disgraced financier Allen Stanford have been raised after it emerged through Wikileaks that US diplomats had suspicions of Stanford being linked to "bribery, money-laundering and political manipulation" as long ago as 2006.

A leaked mail from Mary Kramer, the US ambassador to Barbados, to the US State Department regarding a meeting with Stanford on April 21, 2006, more than two years before his deal with the ECB, flagged the high levels of concern with his business activities even at that time.

"Embassy officers do not reach out to Stanford because of the allegations of bribery and money laundering," the mail noted. "The ambassador managed to stay out of any one-on-one photos with Stanford during the breakfast. It is whispered in the region that Stanford facilitates resolution with significant cash contributions."

In an accompanying explanatory note, Stanford was described as a "controversial Texan billionaire who has made significant investments in offshore finance, aviation, and property development in Antigua and throughout the region. His companies are rumored to engage in bribery, money laundering, and political manipulation."

The revelations will further embarrass the ECB which was forced to admit after Stanford's collapse it had not conducted the necessary levels of due diligence into his business affairs before entering into deals with him but had made decisions based on whether Stanford had the money to pay, rather than any assessment of his activities.

It was only when the Securities and Exchange Commission (SEC) filed charges that the contract was cancelled, although the ECB continued to argue it could not have been expected to know about the concerns surrounding Stanford's business operations and could only conduct due diligence on the basis of information in the public domain.

Stanford's empire came crashing down in February 2009 when the SEC charged Stanford and three of his companies with a "fraud of shocking magnitude". He was arrested by the FBI in June 2009 and has remained in custody ever since. Stanford has pleaded not guilty and will stand trial early next year.