The Fianna Fáil Leader Micheál Martin has repeated his invitation to the Sinn Féin Leader Gerry Adams for a head-to-head debate on the Fiscal Treaty.
It comes after the Taoiseach Enda Kenny said he would not take part in a head-to-head debate with Mr Adams on TV3.
The Taoiseach said he does not participate in programmes presented by Vincent Browne.
Mr Martin said: "It is quite clear that Gerry Adams is not serious about debating the real issues in this Treaty directly with the 'Yes' side.
"After refusing my invitation for a head-to-head debate last weekend, Deputy Adams issued an invitation to the Taoiseach that he knew was unlikely to be accepted.
"If Mr Adams is really willing to defend his position on this Treaty, he would welcome an opportunity for a head-to-head debate with the opposing side. As party leaders, we have a duty to answer questions about the position we have taken on this Treaty and to be open and honest about what a 'Yes' vote and a 'No' vote means for Ireland.
However, Sinn Féin's Pearse Doherty has said the Taoiseach is running scared.
Mr Martin said: "Sinn Féin have said that the Fine Gael Leader has a duty and a responsibility to “step up to the mark” and debate the contents of this Treaty. We agree.
"The same rules must apply to Gerry Adams, and to the leaders of all political parties involved in the campaign."