Mounting allegations of IRA involvement in the £26.5m Belfast bank robbery and growing police suspicions of a much wider involvement of the Irish republican movement in money-laundering operations are threatening Sinn Féin's legitimate fundraising operations in the US, say diplomatic sources in Washington.

According to Irish officials, the fact that the onslaught on the alleged criminal activity of Irish republicans is being led by the Irish government is fuelling dissent among supporters of Sinn Féin, the IRA's political wing, across the Atlantic.