Delegates are meeting at the Convention Centre in Dublin
Sinn Féin says it is the voice of Opposition - even if Fianna Fáil wants to stay there.
The Sinn Féin Ard Fheis continues in Dublin today after last night delegates heard criticism of Micheál Martin for potentially facilitating the return of Enda Kenny to the Taoiseach's office.
Delegates passed a motion calling for the abolition of water charges, adding that any fig leaf of compromise between Fine Gael and Fianna Fáil would be opposed.
The Ard Fheis - which is taking place in Dublin's Convention Centre - is set to conclude with a televised address from party leader Gerry Adams tonight.
The Sinn Féin President yesterday hit out at the Fianna Fáil leader, saying talks that could see Enda Kenny back in office were a breach of election promises.
Meanwhile, Sinn Fein's deputy leader Mary Lou McDonald says the two big parties need to realise her party is not going away.
"Sinn Féin is the leader of the Opposition - the leader of opposition to bad government," she said.