Working class Catholics in the North were "anti-authority and anti-everything", the late Archbishop of Armagh Cahal Daly said.
Secret State files, just released under the 30-year-rule, show the one-time head of the Catholic Church in Ireland blamed a deep scepticism among some of his flock on the SDLP.
In remarks made to a senior Irish government official in 1986, he said the party, then under John Hume, had made no serious effort to challenge Sinn Féin in Catholic ghettos.
The result was a wary response to the then fledgling Anglo-Irish Agreement in areas such as west Belfast, according to the ex-primate, who was Bishop of Down and Connor at the time.
Gerry Adams was "the working class hero" and the SDLP "count for nothing", he said.
The remarks were made during a secret meeting with David Donoghue, an Irish government negotiator in Anglo-Irish talks who went on to become ambassador to the UN.
Notes of the meeting in February that year show Bishop Daly believed middle-class Catholics strongly supported the new agreement.
"In the working-class Catholic ghettos of west Belfast, however, where people are 'anti-Establishment, anti-authority and anti-everything', the mood is one of deep scepticism," he remarked.
Bishop Daly "blames the SDLP for having made no serious effort in the past to penetrate West Belfast and to challenge Sinn Féin's monopoly there."
The soon-to-be cardinal also took aim at unionist leaders for rising loyalist violence and sectarian murders.
"Bishop Daly blames the 'totally irresponsible' attitude of unionist politicians for much of this militancy," the notes state.
"There are moderate voices in the unionist camp but they 'cannot be heard about the din' (a metaphor which he applied also the SDLP in West Belfast."
This had the effect of Catholics "in the ghettos" turning "all to easy to the Provos for their protection".
He said there was considerable anger that then DUP leader Ian Paisley had managed to take control of the unionist community and made then UUP leader Jim Molyneaux "look like a small boy".
Turning his attention to then Secretary of State Tom King, Bishop Daly dismisses the senior Tory figure as a "totally unimpressive politician".