Mary Lou McDonald has dubbed Fianna Fáil as “Sinn Féin lite” for borrowing the election promise to scrap water charges at the party's Ard Fheis.
The Sinn Féin deputy leader has said Micheál Martin must now stand by that election pledge.
“Fianna Fáil was never serious in its manifesto promise to scrap water charges,” said McDonald.
“They were simply positioning themselves for the election campaign – a soft, kind Fianna Fáil.
“If imitation is the sincerest form of flattery, then we Sinn Féiners are only scarlet from the compliment they pay us by borrowing our policies.”
She went on to tell Fianna Fáil leader Micheál Martin.
“We will not assist Micheál Martin and Fianna Fáíl as they put Fine Gael back in government,” said McDonald.
“Not a chance. They are the problem, not the solution.
“They have turned their back on the people, we will stand by the people and with the people.”
Finance spokesman Pearse Doherty has said politicians need to realise there are people's lives behind the economic numbers.
“The people of Ireland have been locked out of their own future”, said Doherty.
“Sinn Féin will tackle this head on through its economic and social policies. Our policies are not made up merely of numbers and statistics, of GDP and bond yields, although of course these are important.
“You cannot treat a hospital bed the same way as a mobile phone. You cannot have an economic policy that treats social cohesion as something that just gets in the way.
“The problems we face as a people are far too great, they run way too deep, to be fixed with such empty and futile gestures as tax credits and modular homes.”
Sinn Féin Party President Gerry Adams will deliver his keynote address tonight.