Minister for Transport Leo Varadkar has said his party has a duty to inform people "what Sinn Fein is really about".
Sinn Féin has more than doubled its seats on local authorities so far, but Leo Varadkar says people should be aware of what they have implemented in the North.
"The way trends are continuing, they may well come into second place, or first place," he said.
"I think there's a duty on us to tell people about what the SF alternative is really about: what they've done in Northern Ireland, and the horrendous austerity that they've imposed on Northern Ireland, the way that pay is so much lower there."
Mary Lou McDonald said that the Sinn Féin vote in the North speaks for itself.
“Sinn Féin went to the North as you know a day before we voted here in the south, and we took out the largest vote of any political party,” she said.
“So the people who live in the North, the people who elect Sinn Féin as the largest political party delivered a very different verdict on our performance in Government than the verdict that Fine Gael and the Labour Party received.”