The Manx government has been asked to ensure that the island's financial institutions are not involved in aiding breaches of criminal or tax laws in other jurisdictions.
The call comes from the Celtic League, a body which fosters cultural links among these islands and Brittany, and follows the detention of a key witness at the Flood tribunal at Dublin Airport with £300,000 in cash and cheques which he allegedly withdrew from banks in the Isle of Man.
The league, which has branches in England, Scotland, Wales, Ireland and in Brittany, has been vociferous on the Tuskar air disaster and the Sellafield nuclear reprocessing plant. It has also campaigned against money laundering.
In September 1998, the Celtic League wrote to the Irish authorities to express its concern that the gardai were "encountering obstruction from some financial institutions" based on the Isle of Man.
The league, which says it was told at that time by Manx treasury spokesmen that "the days when people could walk into Manx banks with suitcases of money and not attract attention were over", says it now appears "as if people from other jurisdictions can walk out of Manx banks with suitcases of money without attracting attention".
Mr J.B. Moffatt, secretary general of the Celtic League, told The Irish Times that if the Manx authorities were not involved in the undercover operation leading to the arrest, then an urgent inquiry should be instituted.
"Of course it may well be that the events which unfolded are the result of co-operation between the Garda and their Manx counterparts and if this is the case then the Manx government should as a matter of urgency make this clear.
"The Manx regulatory authorities (should) establish what involvement, if any, financial services in the Isle of Man had with individuals identified in the course of the Flood tribunal's deliberations, and if this involvement in any way aided or abetted a breach of the laws of the Irish Republic", he concluded.