Taoiseach Brian Cowen has said it is time to 'get real' about the consequences of a second No vote on Lisbon.
Mr Cowen was answering questions on the Lisbon Treaty at the Joint Oireachtas Committee on European Affairs.
He said that it would be 'naive' to say there would be no consequences of a second no vote, as Ireland would be standing in the way of a treaty to make the EU more efficient.
The Taoiseach has said the Lisbon Treaty was fundamental to where Ireland is going - and should not be regarded as an optional extra.
Meanwhile, a group representing 135 local authority politicians who oppose the Lisbon Treaty have launched their campaign.
They claim the treaty will lead to more public services being provided by private companies.
In Germany, politicians have approved legislative changes which pave the way for ratification of the treaty.
The Bundestag lower house of parliament backed the changes after Germany's highest court demanded in June that the Chancellor Angela Merkel's government tweak legislation on the EU treaty to make it comply with the German constitution.
The Bundesrat upper house must still vote in favour of the changes before Germany can ratify the treaty.
Ireland, the Czech Republic and Poland have yet to approve the treaty.
