Three leading US investment funds who bought bankrupt Seán Quinn’s businesses in Cavan and Fermanagh have demanded the former billionaire speaks out against an “escalating” campaign of violence and intimidation.

Brigade Capital, Contrarian Capital and Silver Point Capital said the attacks on its operations and on local management "adversely impact our willingness to continue to invest and grow".

However, in an email to local management last month, the investors in Quinn Industrial Holdings Limited (QIHL) equally insisted that "they will in no way be intimidated".

Mr Quinn is currently a €500,000-a-year adviser to the company.

A series of attacks and vandalism on factories, homes and wind turbines has prompted investigations by the Garda Síochána and the Police Service of Northern Ireland.

The Danish ambassador has also called on the Department of Justice for protection for Danish engineers installing Vesta wind turbines for QIHL along the Border.

Despite Mr Quinn’s wish to regain control of the companies, the US hedge funds made clear that they currently have “no appetite for Seán’s role expanding beyond the advisory relationship already in place”.

He must “rectify” his relationship with local management and “take an active approach, demonstrable over time” against “ increasingly negative activity” if he is “to become bankable in the finance community again”, their email stated. Recent developments “have done nothing but move Seán further away from his goal” and “are downright detrimental” to his own interests, the US investors declared.

In a meeting last month, Mr Quinn's adviser, Ronan Barrett, told them "Seán has grown increasingly uncomfortable" with his role as an adviser and " has a strong desire to acquire ownership".

The email, seen by the Enniskillen-based Impartial Reporter, accuses Mr Quinn of trying to foment division among the local senior management team, which is led by his former deputy, Liam McCaffrey.

Mr Quinn did not respond to requests for comment.