The INLA, one of the deadliest and most ruthless paramilitary groups in the Northern conflict, is preparing to disband.

The organisation, which has held secret talks with the British, says the time is right "to leave the stage".

A keynote address outlining the INLA's future is expected to be made this afternoon in Bray, Co Wicklow at a commemoration for Séamus Costello, the group's founder.

The speech is due to be delivered by Martin McMonagle from Derry, a leading member of the INLA's political wing, the Irish Republican Socialist Party (IRSP).

The INLA's intention to disband will be welcomed by the British and Irish governments and Sinn Féin as strengthening the peace process.

While the INLA won't announce decommissioning, it hasn't ruled this out in future. Although it opposes the Belfast Agreement and the Police Service of Northern Ireland, it says current political conditions aren't right for republican paramilitary groups to exist.

It says disbandment will allow the IRSP to grow. Future negotiations over decommissioning may involve demands for both governments to release INLA prisoners and also for funding for schemes to help ex-prisoners.

Despite the INLA's intentions, the Real IRA and Continuity IRA last night vowed to continue their campaigns. The Real IRA, which murdered two British soldiers at Masser­eene in March, said it had no intention of calling a ceasefire or disbanding.

"We are strengthening our ranks," a source said. "What the INLA does is its business. Our position is simple – while the British occupy Ireland, Irish people have the right to armed resistance."