Former nationalist MP Seamus Mallon thought Gerry Adams's speeches in the early 1980s were being written by a priest.
During a particularly vicious phase of the troubles, the SDLP figure claimed the Sinn Fein president's statements were well put together but not penned by him.
In Government documents released under the 30-year rule, Mr Mallon said he thought a respected Belfast priest, Fr Des Wilson, was the brains behind the republican leader's speeches.
The State papers show the unsubstantiated claim was carried back to the Department of Foreign Affairs in Dublin in late 1983 following one of its fact-finding missions in the north.
Diplomat Daithi O Ceallaigh reported back on meeting Seamus Mallon.
"He referred on a number of occasions to the speeches made by Adams in recent times which he thought were very well written," he said.
"He claimed that Adams could not himself write such speeches and said it was his guess that they were being drafted by Fr Des Wilson."
Fr Wilson, originally from the Ormeau Road in Belfast, is well regarded in communities in the west of the city after setting up the Springhill Community House in Ballymurphy and educating young disadvantaged people.
He has written a column for the Andersonstown News for more than 30 years.
Mr Adams has spoken highly of Fr Wilson, describing him in the same breath as the late Fr Alec Reid as a tenacious peacemaker. In this year's Sinn Fein ard fheis he put him in the same bracket as Methodist leader Harold Good and trade unionist Inez McCormack.
He credited him, alongside Fr Reid, as a key facilitator in ending inter-republican disputes in the 1970s and also helping to open dialogue with loyalist paramilitaries.
In one of his books, Mr Adams referred to Fr Wilson resigning from clerical positions in the church over the use of resources.
The report in the State papers, marked confidential, was based on a visit between November 29-30 1983.
It also noted that Mr Mallon was angered that his party leader, John Hume, was travelling to the US when an important debate about Northern Ireland was planned for Westminster.
"Mallon said that he would continue to speak out on security matters despite his worries about his own safety and that of his family," the report says.
"He was clearly very preoccupied about his future."