Mr. Quinn has repeatedly condemned the intimidation and attacks, including the assault on Mr. Lunney .

A statement released by the Quinn family said, “We have had no involvement in the Quinn Group for several years now and are deeply frustrated and angered that our former ownership of those businesses is being associated in any way with such abhorrent acts.”

In a recent rare TV interview, with Britain’s Channel 4 News, Mr. Quinn said that he had “no hand act or part, or no knowledge or no gain” in the attack on Mr. Lunney, and that it had caused him to give up his ambition to regain control of his former companies. “People can say whatever they want about me, but I don’t want to be seen to be the beneficiary of abuse or criminal activity.”

Despite Mr. Quinn’s repeated condemnations, the campaign has continued. Ten days after his TV interview, a masked man wearing a costume associated with paramilitaries fighting British control in Northern Ireland issued a new letter threatening Quinn Industrial’s owners and management.

“This is your last warning to resign to the directors of Q.I.H., obviously you haven’t learned your lesson after what happened to Kevin. If we wanted we could have killed him very easily,” the statement read. “The Quinn family that employed hundreds of people were stabbed in the back and we have the capability and manpower to see this through until the end and achieve a permanent solution.”

Since the assault on Mr. Lunney, the police on both sides of the border have ramped up measures to solve the string of crimes. The Irish police force, An Garda Siochana, said that while no one had been charged at this time it had sent several files to prosecutors, and the Garda commissioner, Drew Harris, who was previously deputy chief constable of the Police Service of Northern Ireland, said he was happy with the progress being made.