MPs probing claims that vital intelligence about the Omagh bomb was deliberately held back are to quiz the senior official who investigated the matter.
Intelligence Services Commissioner Sir Peter Gibson said information on the Real IRA bombers was shared with police but could not have stopped the 1998 Northern Ireland attack.
He appears before the Northern Ireland Affairs Committee of MPs on May 13th following the BBC
Panoramaprogramme which made the original allegations.
In his report Sir Peter said details from telephone intercepts were passed on promptly and fully and in accordance with proper procedures.
A total of 29 people died when the dissident republican car bomb exploded in the Co Tyrone market town.
A spokesman for the Northern Ireland Affairs Committee said Sir Peter would appear as part of their "investigation focusing on the sharing of intelligence relating to the bombing and lessons learnt in the intervening 10 years".
A Panorama programme claimed intelligence officers based at Government Communications Headquarters (GCHQ) had monitored the bombers' phone calls, but failed or refused to pass information to Royal Ulster Constabulary (RUC) detectives hunting the killers in the days following the attack.
Following the programme last September, British prime minister Gordon Brown commissioned Sir Peter to conduct a review of all intelligence material stemming from the bombing.
PA