Mary Lou McDonald has called for a complete shutdown of non-essential services in order to tackle Covid-19.
The Sinn Féin leader said that after events at the weekend, the government should implement a ban on gatherings and workplaces that cannot safely implement social distancing.
A number of incidents of mass gathering were reported over the weekend, including at the Sally Gap in the Wicklow Mountains, and at a beach car park at Lahinch in Co Clare, with the gardaí eventually closing both in order to discourage people from entering the area en masse.
"Social distancing in the first instance needs to be a policy and approach that's championed by every arm of the state, and in real terms, the only way that that can be done is to now close all non essential business," she said.
"To ensure everybody is safe, to ensure that we prevent to the greatest extent the transmission of this virus, and by extension that we give some relief, and time to our health services when they are stretched to capacity.
"I think at this stage delay is dangerous.
"I think it is unacceptable to leave tens of thousands of workers in conditions that are not safe, where they know they risk contracting and transmitting this virus, where they risk bringing this virus home to their families and their children."
The announcement by Ms McDonald, made in Dublin, is expected to be mirrored in Belfast on Monday afternoon, in which it will be announced by First Minister Arlene Foster and Deputy First Minister Michelle O'Neill, that all non-essential businesses will shut.
Sinn Féin have repeatedly called for an "all-island" approach to the crisis as cross-border implementation has already created a considerable amount of confusion regarding schools closures and approaches to testing.
Sinn Féin are also calling for an income support scheme and for the government to go further than they have done in social welfare reforms for those who have been left out of work due to the pandemic.
"Rather than telling us where the money won't come from, he needs to now apply himself to securing the necessary funding, because this income support scheme needs to happen," she added.
"The Dail needs to meet as a matter of urgency because I understand that legislation will be required for the measures that I have outlined in terms of income support.
"Certainly if I were Taoiseach, I would be announcing today at the shutdown of all non essential business.
"I think it's the only responsible course of action, and I think the the workforce of Ireland and the families of Ireland at deserve that kind of leadership at this time."
Essential businesses, according to Sinn Féin are supermarkets, fuel stations, pharmacies and emergency services.
Restaurants who are able to abide by social distancing measures in order to provide takeaway food should also stay open according to Ms McDonald.