The British government drew up a secret plan in 1972 to forcibly expel hundreds of thousands of Catholics from Northern Ireland, according to documents released today.
It also sought to redraw the Border to create a Protestant-only enclave, the documents released to the Public Record Office under the 30-year rule show.
The hitherto top secret file said officials had discussed the feasibility of redefining the border, "and compulsory transfers of population within Northern Ireland between the Six Counties and the Republic."
The North could be partitioned into two zones, one Protestant and one Catholic. The Catholic area could then be integrated into the Republic, leaving the Protestants in an "avowedly sectarian statelet".
Under it, more than 300,000 Northern Irish Catholics would have been forcibly evicted from their homes, and 200,000 Protestants would have had to evacuate the area ceded by Britain to the Republic.
Officials warned that they would face "great resistance" and could only been forced through the "completely ruthless" use of force.
The move to consider drastic remedies came against a background of escalating violence, which claimed almost 500 lives in the course of the year, prompting fears among that the province was on the brink of civil war.
The plan was presented to Conservative leader Mr Edward Heath on July 23rd, 1972, two days after "Bloody Friday" - when 11 people died and 130 were injured in a series of bomb attacks in Belfast following the collapse of a brief IRA ceasefire.
In his preamble to the document - marked "Top Secret: UK Eyes Only" - Cabinet Secretary Sir Burke Trend said it was "explicitly addressed to a situation in which we are on the point of losing control of events unless we take very severe action indeed".
"About one third of the population...would be on the move," the document said. "Such a massive movement would not be peacefully accomplished; great resistance could be expected from many of those who should move.
"A great deal would depend on the extent to which we could continue to count on local co-operation as regards the maintenance of essential services and on the loyalty of the RUC," he added.
Throughout the document officials made it clear that they were "extremely doubtful" that such a policy could work, warning that it would wreck Britain's reputation abroad and could even lead to a collapse of the pound.
"Unless the Government were prepared to be completely ruthless in the use of force, the chances of imposing a settlement consisting of a new partition together with some compulsory transfers of population would be negligible."
PA/AFP