Quinn lobbied EC in 1985 on 'damage' from Irish policy
Sean Quinn lobbied the European Commission after claiming that Irish economic policies were threatening his business.
He accused the government of protectionism after it said State contracts would be awarded only to firms using Irish cement.
He wrote to Brussels in 1985, warning that the continued prosperity of his company was reaching a critical level.
Mr Quinn, who went on to become Ireland's richest man, claimed a covert "buy Irish" campaign was impacting on his trade.
In 1983, the Irish Government had introduced a ministerial directive ordering contractors not to use products bought outside the Republic.
It followed complaints about the high level of building materials being imported from Northern Ireland.
It noted that Northern Ireland producers were in receipt of grant aid, giving them an unfair advantage over southern plants that did not receive grants. However, Mr Quinn claimed the policy was affecting his quarry business in Derrylin, Co Fermanagh.
The Quinn letter was revealed by the UK yesterday under the 30-year rule.
In July 1985, he wrote to the European Commission out- lining his concerns.
"We would ask you to investigate the complaint that materials from Northern Ireland may not be used for the construction industry within the Republic of Ireland, with particular emphasis on concrete products," he wrote.
Mr Quinn said cement used at his works was sourced from Cookstown, Co Tyrone.
He cited examples where products manufactured by his company were banned on Irish government contracts.
These included projects at Loretto Convent School in Letterkenny, Co Donegal; a housing scheme in Granard, Co Longford; and Ballyconnell fire station in Co Cavan.
Mr Quinn said 45pc of his trade was with the Republic, and feared the pressure to "buy Irish" would hit his business. Similar concerns were raised by Concrete (Northern Ireland) Ltd, in Dromore, Co Down.
A memo, compiled by a Northern Ireland Office official, concluded: "If the above is accurate, it seems quite clear that there is a strong case of economic protectionism being pursued in the Republic to prevent Northern companies taking any business."