It was the year that ended with the Enniskillen bombing, part of a seemingly endless IRA campaign, and a time when Gerry Adams was still politically persona non grata.

But while Sinn Féin remained in the political cold in 1987, newly declassified Irish government files reveal that fringe contacts between Labour and the IRA’s political wing may have helped nurture moves by Adams to shift the group from violence years before the Good Friday agreement.

They reveal the Sinn Féin leader was banking on a general election victory in that year, or after, by a Labour party becoming re-energised under Neil Kinnock. The documents show Adams was intending to “sell” a plan to hardliners in the IRA that would see the new UK government declaring its intention to withdraw from Northern Ireland. The way in which Sinn Féin might have been influenced by the Labour MPs who risked meeting the party at the time are also revealed in notes taken by an Irish government official who spoke to a Belfast solicitor and confidant of Adams.

The notes state: “Adams would, of course, want a stated time scale – ‘maybe 25, 40 or even 50 years’. If he were to get something which he found acceptable, he would undoubtedly be able to sell it in turn to the Provos.”

Writing a decade before the IRA’s leaders eventually downed their weapons, they add: “It might take some time, and there would be a lot of suspicion and scepticism to overcome, but eventually he would carry the Army Council with him.”

The Irish official drew up the notes on the basis of talks with PJ McGrory, doyen of Belfast’s criminal solicitors, who died of a heart attack in 1994, aged 71. The discussions took place soon after a Labour delegation consisting of its Northern Ireland spokesman, Peter Archer, the MP Stuart Bell and two NEC members met Sinn Féin councillors in Belfast in January 1987.

The newly released files suggest early contacts may have shaped embryonic Republican moves towards a peaceful path

Under pressure over that meeting, which he had refused to participate in, Kinnock had said that “it was as well we have the widest possible encounter with people who are democratically represented”.

While the meeting was widely criticised, the newly released files suggest that those early contacts may have shaped embryonic republican moves towards a peaceful path.

“Adams would clearly have an interest in nurturing any movement in Labour towards a policy of British withdrawal. McGrory told me that in their recent conversation Adams indicated to him that he was ‘thinking along those lines at present,’” they state. They add, however, that the republican leader remained suspicious of Labour in the light of its actions and stance on Northern Ireland while in government in the mid-1970s.

The notes go on to say that Adams confided he “personally felt entitled to decide that the armed struggle was undesirable at a given point in time”. McGrory took this to mean that Adams “disapproves of individual IRA atrocities”.

The Sinn Féin leader confided, however, that he could never say so in public – “the Army Council gives me only so much leeway.” Jonathan Tonge, a professor of political science at the University of Liverpool, told the Observer the files provided clear confirmation of how Adams was trying to develop a peace strategy in the 1980s.

“Most of the focus on Adams’s peace strategy has been about the attempts of Adams to bring the IRA to ceasefire and to cultivate pan-nationalism as the means of selling peace, getting the SDLP, Irish government and Irish America onside,” he added.

“These documents indicate a third strand to Adams’s efforts, involving a bid to break Conservative-Labour bipartisanship on Northern Ireland. Adams was encouraged by Labour’s ‘unity-by-consent’ policy on Northern Ireland. His strategy was to get the Labour party to stress far more forthrightly its desire for Irish unity, to encourage the IRA to believe in the possibilities of politics.

“This aspect of his peace strategy had a limited shelf life, however. When Tony Blair became Labour leader in 1994, he dropped the unity-by-consent approach and sacked its main exponent, Kevin McNamara. By that point, however, the pan-nationalist aspects of Adams’s approach were paying dividends.”