Representatives of the Save Tara - Skryne Valley group were told they should moderate their presentation and apologise for "innuendo" during an Oireachtas Transport Committee hearing yesterday.
In strongly-worded exchanges, the chairman of the committee, Mr John Ellis TD, told Dr Muireann Ní Bhrolchain that unless she and fellow campaigner Mr Vincent Salafia refrained from making allegations against named individuals the hearing would have to be adjourned.
Mr Ellis also warned the group that it should not make allegations against the clerk and staff of the committee, and should confine commentary to transport issues.
Mr Ellis also complained of "misinformation" in relation to the number of letters received by the committee on the motorway issue, and "innuendo" which he said was contained in the group's presentation.
A number of other committee members also complained about the tone of the presentation, with Sen Timmy Dooley (FF) claiming it undermined the committee "by questioning our integrity".
He added: "I object in the strongest possible terms to the kind of language being used."
Sen Dooley said the people who came before the committee to give evidence must accept the guidelines laid down by the committee if they wanted to be heard.
Mr Peter Power TD (FF) also objected to the presentation, saying he felt "a line had been crossed".
Objections from the TD and senators began almost as soon as Mr Salafia began his presentation, and having mentioned the name of Mahon tribunal witness Mr Frank Dunlop in connection with the controversy, Mr Salafia was asked to withdraw "the innuendo" and apologise.
Mr Salafia explained that the group was concerned it had been "excluded" from a recent Environment Committee hearing.
The group said it had supplied the Transport Committee with about 2,000 letters which objected to the motorway.
However, this was rejected out of hand by Mr Ellis, who said the committee had received about 200 such letters.
When Mr Salafia said he wished to "disagree completely", a number of TDs and senators said Mr Salafia had cast a slur on the clerk and staff of the committee.
Mr Ellis said what was being suggested was that essentially letters which were intended for the committee had not been passed on by the staff.
Sen Dooley also objected, saying the committee had the "utmost confidence" in the clerk and staff "and their ability to count".
However, independent senator Mr David Norris asked if it was fair that the committee should subject those who give evidence "to a fusillade of abuse", adding that "it is not appropriate".
Continuing the group's presentation, Dr Ní Bhrolchain was repeatedly advised by Mr Ellis that she should refrain from delving too deeply into the archaeological and environmental impacts of the road as the committee was concerned only with transport issues.
"How can we discuss this," she asked, before adding: "Since when did A&E (archaeology and environment) become dirty words?"
