The Fine Gael and Labour leaders warned against outside interference in the EU treaty referendum campaign.
Enda Kenny said that "when one considers that every headbanger in Europe will probably be in Ireland when the referendum takes place, and that they will be well-resourced in many cases, one will realise that there may be some very exciting public meetings".
Eamon Gilmore said he agreed with Mr Kenny that it was not desirable that "Ireland should become the focus for over-anxious people from outside the State".
He added that he was referring to those who supported and opposed the treaty.
"Irish people will want to decide on the treaty and the referendum without outside interference.
"We should try to take up a minimum number of the offers of assistance we undoubtedly will receive during the campaign, even if they are welcome and well-intended . . . We do not want the referendum campaign to become a battleground for people who do not have an opportunity to vote on the treaty in their own countries."
Sinn Féin spokesman Aengus Ó Snodaigh said he wanted to have an open and honest debate.
"I do not want headbangers of any type, particularly those on the Yes side, including Commissioner Charlie McCreevy, interfering in this referendum.
"The EU commissioner, from Ireland, who was chosen by the Taoiseach, supposedly to represent the State in a role akin to a civil servant, had the gall to state recently that if the State voted No to the treaty, it would be turfed out or excluded."
Mr Ó Snodaigh said that this was "scaremongering".
Speaking during a series of statements on the EU Council meeting in Lisbon, Mr Kenny and Mr Gilmore pledged that their parties would fully support the referendum.
Mr Gilmore said that he welcomed Taoiseach Bertie Ahern's commitment to consult the Opposition parties on the manner in which the referendum campaign would be organised and presented to the people.
The Taoiseach repeated his belief that, following a full and engaged debate, the people of the Republic would approve the treaty.
"I believe they will do so, not only because it serves our national interest, but also that of the entire EU."
