HSBC has said it is cooperating with Belgian authorities after a number of dawn raids were carried out on diamond dealers in Antwerp as part of a sprawling tax evasion investigation which focuses on the British High Street giant.
The dealings between gem traders and bankers have come under increased scrutiny amid fears they are being used to hide wealth from tax authorities.
Last month there were reports that of almost 3,000 secret Swiss accounts at HSBC on the list obtained by former Geneva-based HSBC employee Herve Falciani, 70 per cent were held by diamond dealers.
It is the latest twist in a criminal inquiry that has dragged on since 2008 after Falciani allegedly stole the records of HSBC customers suspected of dodging tax.
This became known as the Lagarde List after the then French finance minister Christine Lagarde, who passed it on to Greek officials to help them crack down on tax evasion.