Former taoiseach Garret FitzGerald offered to hold a referendum to remove the territorial claim on Northern Ireland in return for an Irish role in policing the North, according to British government documents released today.

The 1984 files also show former British prime minister Margaret Thatcher considered redrawing the border to move mainly Catholic areas into the Republic of Ireland.

During the year, Dr FitzGerald offered to hold a referendum to remove Articles 2 and 3 of the Constitution, which claimed Northern Ireland.

Although he had told British officials, he had only told a small number of Cabinet colleagues about the idea and some members of Government would oppose such a move.

He told Mrs Thatcher that it was feasible because a united Ireland was no longer regarded as a serious prospect, but he wanted a role for Dublin in policing the North in return.

That was a price the British government was not prepared to pay. It doubted, along with SDLP leader John Hume, if Dr FitzGerald could carry a referendum on the issue.

Meanwhile, in relation to the idea of redrawing the border, Northern Secretary Jim Prior told Mrs Thatcher this would cause enormous difficulties, both practical and political.

He said such draconian measures could only be considered in the event of civil war.

Britain is moving by stages to a 20-year release period for sensitive government documents, which is why the files for 1984 were made public today.