The INLA has the Provisional IRA on the run - behind bars. An INLA leader delivered a vicious beating to the Provos' last remaining inmate in Portlaoise, spy Kenny Donohoe.
The Provo was left so traumatised by the hiding that he has turned to the Continuity IRA in the maximum security jail for protection.
The PIRA leadership has threatened to kill the INLA man who carried out the assault but sources say "he is laughing the whole thing off".
"They're not the first or last people to threaten to kill him. He's not a bit worried," the source said.
Prison staff at Portlaoise maximum security jail are already on high alert following renewed tensions after the INLA and CIRA caused disturbances and threw human waste at the governor.
Meanwhile, sources said Kenny Donohoe is a worried man after the assault on him, which has caused huge embarrassment for the Provo leadership.
"It shows they can't look after their own any more. That is a huge embarrassment to them," said a source.
Donohoe (29) is a convicted IRA member and is believed to be the is the last remaining provisional prisoner at the midlands jail.
He was jailed for four years for membership of the IRA in 2004. He was also the subject of a garda investigation into a spy network set up targeting TD's. During his trial along side his co-accused Niall Bennett (36) the court heard that gardai found a list of TDs, including three former Justice Ministers, at Bennett's home.
Paramilitary prisoners from the Real IRA and INLA joined forces to challenge staff at Portlaoise in a dispute over the searching of cells.
The dirty-style protest involved full chamber pots being thrown at staff, forcing the closure of a food preparation.
And tensions at the prison were only brought under control when two inmates were released from segregation cells they were being held in.
The disturbance began on Sunday morning when the cells of a number of INLA inmates were searched on the E4 landing of the maximum security jail. A makeshift knife was found in one of the searched cells. The search and seizure led to tempers being flared.
The INLA inmates were unhappy that the searches had taken place claiming they had been singled out for "special treatment".
A protest resulted in prisoners throwing the contents of their chamber pots on to the landing of their wing. When other prisoners were asked to clean the area, they were threatened by the INLA group.
A spokesman for the Irish Prison Service said the protest was "minor" and "non violent" and that it had been dealt with quickly and in a non-confrontational manner.