An MI5 agent handler has said he warned police the INLA were planning to kill loyalist leader Billy Wright inside the Maze Prison.
LVF leader Billy Wright was shot dead in the Maze Prison in 1997
The handler said he told police of the move in April 1997, eight months before Wright, 37, was murdered.
He made the comments during an inquiry into the death of the loyalist Volunteer Force leader.
The INLA were "deeply unhappy" about Wright's proposed move to H-Block Six, occupied by them, the inquiry heard.
The agent told his handler said that if it happened, the INLA would try to kill Wright at the earliest opportunity.
The agent thought the most likely method would have been to use a hypodermic syringe filled with poison.
Former Northern Ireland Secretary Paul Murphy announced the public inquiry into Wright's killing in November 2004 following allegations of security force collusion in his murder.
The inquiry is expected to last for some time.