Former Justice Minister David Ford failed to enforce a deal to limit controversial prisoner strip-searches because he was probably beholden to the DUP, a parliamentary watchdog has been told.
An agreement struck in 2010 vowed to ease contentious measures, including full-body searches, at Maghaberry, Northern Ireland's only high-security jail.
But one of the deal-brokers, leading trade unionist Peter Bunting, said political interference helped ensure it was never fully implemented.
"I do believe there is interference in the sense, in our view, that the then-Minister of Justice was probably beholden to the likes of the DUP for his position, and I think that probably resulted in him lacking the resolve to tackle this matter head-on," Mr Bunting told a parliamentary committee in Dublin.
But Mr Ford rubbished the claim and said: "I utterly refute any suggestion that I was beholden to the DUP.
"I had DUP and Sinn Fein support to be elected minister, but I made it absolutely clear I was acting on an Alliance agenda, which they accepted before they voted for me."
Mr Ford, who stepped down as leader of the Alliance Party last month, added that the prisoner deal, reached six years ago and backed by both the British and Irish Governments, included an agreement to end threats to prison officers, but they continued on social media almost continuously thereafter.
Two serving prison officers have been murdered since 2010.
Mr Bunting, a key figure in securing the decommissioning of INLA weapons, said both himself and another mediator, Conal McFeely, met Mr Ford's successor, Claire Sugden, in May and were assured of a speedy review on the agreement's implementation.
But he claimed they had heard nothing back since then.
The deal-broker said that strip-searches were being used as a "tool to suppress people" in the Roe House wing of the prison, where republican inmates are housed. There is both a sectarian attitude and there is political interference towards these people," he added.
The Joint Committee on the Implementation of the Good Friday Agreement was told readily available technology has done away with the need for invasive body searches.
However, Mr Bunting said the practice was part of everyday life in the jail.
Prisoners are also isolated for extended periods - with one inmate being locked up 23 hours a day for five years - and denied education, he added.
Treatment of dissident republican prisoners in Maghaberry has long been a source of contention. Some say they are forced to suffer inhumane and degrading treatment, while others say they receive favourable treatment compared to the rest of the prison population.
Mr McFeely said that the "question of political interference had to be answered".
Senator Frank Feighan, who sits on the committee and who visited the prison, said there was "a lot of pettiness" involved in resisting reforms.
"I'm concerned about what you are saying about political interference with the Minister for Justice," he added.
"If that was happening down here, it would be a serious national scandal."