The Nally inquiry team appeared to accept Garda claims without question, but went through a "forensic examination" of the accusations by the disaffected detective sergeant whose claims led to the inquiry being set up, the Labour leader said in the Dáil.
Mr Pat Rabbitte, who had sight of the report into allegations of Garda inaction on the 1998 Omagh bombing, said "it appears there is a significant difference between what the inquiry team was willing to accept from the gardaí by way of evidence and explanation, as opposed to what it accepted from the disaffected detective sergeant".
He pointed out that the team "went through a forensic examination of the sergeant's evidence and highlighted inconsistencies and contradictions.
"However, when it came to the gardaí, a similar level of rigour was not applied and claims by gardaí that were unsupported by evidence were accepted without doubt."
Mr Rabbitte said that "time and again" in the report, reference was made to excellent co-operation between the PSNI and the Garda. But in at least two instances senior Garda officers were quoted as stating that despite the lack of a paper record, "they would have informed RUC counterparts of events such as burnt-out cars being found. The relevant RUC officers cannot specifically recall being informed of these events but stated that if their Garda counterparts said so, it must have happened."
He said that "despite the absence of a paper record and the clear failure of the RUC to recall information being passed to it, the inquiry team accepted this as being the case. On the other hand the disaffected detective sergeant was not at any stage afforded such a benefit of the doubt by the inquiry team." However, he stressed that "I am in no way persuaded of the truth of any of the detective sergeant's allegations, let alone all of them".
Earlier, the Fine Gael leader, Mr Enda Kenny, renewed his call for an investigation along the lines of the Cory inquiries to follow this "preliminary-type inquiry".
Such an investigation, he said, should have the power to interview witnesses on both sides of the Border, including the key witness who was not interviewed by the Nally group.
However, the Minister for Justice, Mr McDowell, dismissed the suggestion that the because the informant was on a witness protection programme, the Garda should have had leverage over the person to persuade him to co-operate and ignore the legal advice given to him not to co-operate.
If the Garda had done that, they could be "accused of attempting to taint or blackmail the person and it would taint the evidence that any person gave to the inquiry after that", Mr McDowell said.
Mr Kenny, who read out the name of each of the Omagh victims, said the Government had made them an "amorphous mass".
But the Nally report was not just another official document waiting to be published. The report was "a reflection on the end of life. For many of them, this report marks a day when they too stopped living and began to exist".
Mr Martin Ferris (SF, Kerry South) said that publishing the report would meet the wishes of the families and strengthen the hand of the Government in calling on the British government to publish a whole series of suppressed reports "from Stalker-Sampson to Stevens and the current report by Judge Cory".