The former minister for justice, Mr Patrick Cooney, is expected to tell the joint Oireachtas subcommittee today that Mr Justice Barron was naive in his approach to investigating the 1974 bombings.
He is also expected to claim that many of the conclusions in the Barron report are not worth the paper they are written on.
Mr Cooney, who held the justice portfolio in 1974, has criticised Mr Justice Barron for basing some of his findings on hearsay and unidentified sources. He has also criticised the absence in the report of a list of suspects.
In a written submission to the sub-committee he rejects Mr Justice Barron's assertion that the government of the day failed to show concern, displayed little interest in the bombings and failed to apply political pressure in the investigation into the bombers.
Meanwhile, a retired British bomb and explosives expert yesterday told the Oireachtas sub-committee that the loyalists who planted the Dublin and Monaghan bombs could not have acted alone and must have had professional help.
Lieut Col Nigel Wylde said the three Dublin bombs had exploded within 90 seconds of each other, a level of professionalism seen in no other loyalist attack before or after 1974.
He also said the ammonia nitrate explosives used were not in the possession of loyalist bombers at the time.
The loyalists only had access to commercial explosives and in very small quantities.
